40.2 Security Sample Configurations Cisco Forum FAQ
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FAQ RevisionsEditors: skj, Covenant, aryoba, Phraxos
Last modified on 2008-11-21 15:11:04

40.2 Security Sample Configurations

·Basic Internet Firewall ACL for Routers without IOS image Firewall feature
·Configure DMZ on routers
·Sample IOS Firewall (CBAC) router configuration
·Sample Configuration of ACL-CBAC-IDS/IPS-IPSec VPN on router
·Zone-Based Firewall Sample Configuration
·Internet access restriction without a proxy server/websense solution?
·Various Site-to-Site IPSec VPN: Cisco, Juniper, Checkpoint, Sonicwall, Zywall
·How do I configure a Zywall/Pix ipsec VPN
·PAT/NAT Router/PIX passing through VPN tunnel
·Private Routing over VPN: GRE over IP Sec
·VPN: Static mappings with overloaded NAT and VPN
·Remote User VPN Connection To Office Network
·Configure router as both Internet router and VPN Concentrator
·Configure PIX/ASA as both Internet Firewall and VPN Concentrator
You probably have a router running basic IOS image without Firewall (FW) feature. You understand that you need a good firewall to protect your network from Internet intruders. There are choices to tackle the problem.

1. Setup a hardware firewall (i.e. PIX Firewall) in front of the router
2. Upgrade the router to run IOS image with FW feature
3. Apply basic Firewall ACL to Internet-facing router interface

Option 1

Check out the following FAQ for sample configuration on setting a PIX in front of a router.
»Cisco Forum FAQ »Internet - PIX - Router - LAN

This setup should be the best approach to tackle the problem. However there are some constraints that might prevent you to choose this option, such as:

1. Financial burden
2. The router has integrated modem (i.e. DSL, cable modem, T1, ISDN) or the router Internet-facing (WAN) interface is not Ethernet interface
3. You do BGP peering with another AS, hence requires a router or layer-3 switch to be the public edge equipment

When the WAN interface router is not Ethernet or your router is BGP peering, then you then have a choice to setup a hardware firewall behind the router, while the router run basic firewall ACL.

Check out the following FAQ for sample configuration on setting a PIX behind a router.
»Cisco Forum FAQ »Internet - Router - PIX - LAN

When you have financial burden, then the only choice is to have the router run basic firewall ACL.

Option 2

Upgrading the router is also a good approach. There are followings that might prevent you to do so.

1. You currently don't have proper Smartnet contract and upgrading the contract might be a hassle
2. The router might run too hot on memory and CPU when the router already run heavy routing
3. Activating any additional features on router (including FW feature) will take the router resources (memory and CPU) that might degrade the router robustness or performance
4. You don't have management control over the router, since there is another party doing so (i.e. your ISP or vendor)
5. You need to meet government agency regulations and using the router as a firewall might not meet such regulations

When you have at least one of those situations, then your best option should be putting a hardware firewall in front of or behind the router.

Option 3

This option is the most economical and might be a quick way to tackle the problem. Keep in mind that

1. This basic Firewall ACL only works on certain situations and certain protocol usages
2. Should you choose to implement this basic Firewall ACL on the router, it is suggested to have additional hardware firewall sitting behind the router for long-term solution

Assumptions on the sample configuration:

* There is Ethernet 0 interface as your LAN interface and Ethernet 1 interface as your WAN interface
* You have a single static Public IP address within your network (the 1.1.1.2/30)
* The Internet default gateway is 1.1.1.1/30
* Your LAN only has 10.0.0.0/24 as internal network and nothing else
* You run public Web and Mail servers (the www and smtp) using the 1.1.1.2 as the public IP address
* The internal Mail server IP address is 10.0.0.2 and the internal Web server IP address is 10.0.0.3
* You also use 1.1.1.2 for Internet browsing traffic from your LAN
* You use your ISP DNS servers to browse the Internet (the TCP and UDP 53)
* Your network daily usage is only browsing the Internet (that only use protocol TCP) and no other protocols used
* You keep logs on potential illegitimate traffic attempts

Following is the sample configuration


Notes:

1. The sample configuration is not intended as full router configuration. It only shows related commands.

2. ACL 100: Inbound Traffic Firewall
* The key of the Firewall ACL (ACL 100) is the "established" keyword
* Internet browsing mean outbound connections initiated from your LAN out to the Internet
* Most common Internet browsing (i.e. open up websites, FTP sites, some Internet video or audio live streaming) only requires protocol TCP
* With Internet browsing, only established TCP packets that are necessary to enter your network as reply packets
* These established TCP packets are TCP ACK (acknowledge) during the three-way handshake or on ESTABLISHED mode (the actual data transfer); and RST (reset to close the connection)
* With "established" keyword, only TCP packet ACK and RST will be permitted to enter your network
* Note that there is no need to specify "access-list 100 permit tcp any eq 53 host 1.1.1.2" since the "access-list 100 permit tcp any host 1.1.1.2 established" would take care reply TCP port 53 (DNS) packets
* This ACL assumes that you have static IP address assignment from ISP (the real static IP; not static by DHCP - read this FAQ for more info »Cisco Forum FAQ »Between DHCP, PPP, Dynamic, and Static IP Address ). If your router must receive ISP IP address from ISP DHCP server, then you need to permit incoming bootps traffic as well. Here is the ACL 100 looks like which incorporates ISP DHCP incoming bootps packets.


3. ACL 101: Outbound Traffic Firewall
* Those TCP and UDP ports are known used by virus/worm, therefore outbound connection to the Internet on such ports should be blocked
* The host IP addresses are "invalid IP addresses" in Internet browsing perspective
* Since only the 1.1.1.0/30 subnet is used as the Public IP subnet, any other IP addresses from different subnet try to go out to the Internet using the router should be illegitimate traffic; hence should be blocked

4. ACL 110: NAT/PAT Traffic Firewall
* NAT/PAT sourcing from any IP address within your Public IP subnet or any IP address other than your internal subnet should be illegitimate traffic and known used by DOS (Denial of Service) attack; hence should be blocked
* No private subnet on the Internet, hence NAT/PAT to those subnets should be blocked as well

5. Blackholing illegitimate traffic
Since there are no other private subnets within your network than 10.0.0.0/24, traffic to other private subnets should go to Null interface (black hole)

More Sample Configuration using ACL as Basic Firewall
»Cisco Forum FAQ »Configure DMZ on routers

feedback form

by aryoba
last modified: 2008-03-29 18:51:44

Suggested prerequisite reading:
»Cisco Forum FAQ »Basic Internet Firewall ACL for Routers without IOS image Firewall feature

On these sample configurations, it is assumed the following occur

* There are at least three network segments; outside (i.e. WAN or The Internet), inside (LAN), DMZ
* These segments are within their own subnet (Layer-3 separation)
* Inside subnet is 10.0.0.0/24 and DMZ subnet is 10.0.1.0/24

Sample #1: Total Separation between Inside and DMZ

This sample assumes the following
* Internet-only access for DMZ
* DMZ cannot access inside
* Inside cannot access DMZ


Sample #2: Restricted Access on DMZ specific services from Inside

This sample assumes the following
* Internet-only access for DMZ
* DMZ cannot access inside
* Inside can access DMZ only for web (TCP port 80) and email (TCP port 25)


Sample #3: Restricted Access on DMZ most applications from Inside

This sample assumes the following
* Internet-only access for DMZ
* DMZ cannot access inside
* Inside can access DMZ on any TCP-based application and DNS (TCP and UDP port 53)
* Note that most applications are TCP-based. Therefore this sample applies to most network



feedback form

by aryoba
last modified: 2008-05-29 10:43:54

When your router is running IOS image with FW feature, you can implement CBAC as a Stateful Firewall IOS-based. With such inspection, the router can inspect inbound traffic from outside such as The Internet to inside the network. The router can also inspect outbound traffic from inside the network to outside. Note that the sample configurations implement outbound inspection on the WAN (Internet) interface that regulate outbound traffic from inside to the Internet.

Typically no inspection is necessary or even needed to regulate traffic between inside or non-Internet interfaces. When there are no public servers hanging off the router and there are only outbound traffic such as Internet browsing (in addition of no inspection between inside interfaces), there should be no reason to implement inspection on inside interface. Therefore it is common practice to implement inspection on the WAN (Internet) interface to regulate outbound traffic when there are multiple non-Internet interfaces on the router and/or there are no inbound traffic.

Inspecting Generic Traffic

version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
!
hostname Router
!
boot-start-marker
boot-end-marker
!
enable secret 5 $1$uOpf$emfDhaV0/UALCYwjF.iHf/
!
no aaa new-model
ip subnet-zero
no ip source-route
!
ip inspect name OUTBOUND cuseeme
ip inspect name OUTBOUND ftp
ip inspect name OUTBOUND h323
ip inspect name OUTBOUND netshow
ip inspect name OUTBOUND rcmd
ip inspect name OUTBOUND realaudio
ip inspect name OUTBOUND rtsp
ip inspect name OUTBOUND sqlnet
ip inspect name OUTBOUND tcp
ip inspect name OUTBOUND udp
ip inspect name OUTBOUND vdolive
ip inspect name OUTBOUND icmp
ip ssh break-string
isdn switch-type basic-net3
!
!
!
!
!
!
interface Ethernet0
description LAN
ip address 192.168.0.16 255.255.255.0
no ip proxy-arp
ip nat inside
!
interface BRI0
no ip address
encapsulation ppp
dialer pool-member 1
isdn switch-type basic-net3
ppp authentication chap pap callin
!
interface Dialer1
description ISP
ip address negotiated
ip access-group 121 in
no ip redirects
no ip unreachables
no ip proxy-arp
ip nat outside
ip inspect OUTBOUND out
encapsulation ppp
no ip split-horizon
dialer pool 1
dialer remote-name Cisco1
dialer idle-timeout 360
dialer string 08089916001 class DialClass
dialer hold-queue 10
dialer load-threshold 20 either
dialer-group 1
no cdp enable
ppp authentication chap pap callin
ppp chap hostname host-username
ppp chap password 7 ****
ppp pap sent-username username-here password 7 ****
!
ip nat inside source list 23 interface Dialer1 overload
ip classless
ip route 0.0.0.0 0.0.0.0 Dialer1
no ip http server
no ip http secure-server
!
!
map-class dialer DialClass
access-list 23 permit 192.168.0.0 0.0.0.255
access-list 121 remark **** Permitted inbound packets ****
access-list 121 deny udp any range 137 139 any
access-list 121 deny tcp any range 137 139 any
access-list 121 deny icmp any any echo
access-list 121 permit icmp any any echo-reply
access-list 121 permit icmp any any time-exceeded
access-list 121 permit icmp any any unreachable
access-list 121 deny icmp any any
access-list 121 permit ip any any time-range TIME
access-list 121 deny ip any any log-input
dialer-list 1 protocol ip permit
!
!
line con 0
exec-timeout 0 0
transport preferred all
transport output all
stopbits 1
line vty 0 4
access-class 23 in
exec-timeout 0 0
login local
transport preferred all
transport input all
transport output all
!
no rcapi server
!
!
time-range TIME
periodic daily 0:00 to 23:59
!
!
end

Inspecting Instant Messaging Traffic

1. Medium Security Policy on Application Traffic

version 12.4
no service pad
service tcp-keepalives-in
service tcp-keepalives-out
service timestamps debug datetime msec localtime show-timezone
service timestamps log datetime msec localtime show-timezone
service password-encryption
service sequence-numbers
!
hostname Router
!
boot-start-marker
boot-end-marker
!
logging buffered 51200 debugging
logging console critical
enable secret 5 ???????????????????????
!
aaa new-model
!
!
aaa authentication login default local
aaa authorization exec default local
!
aaa session-id common
!
resource policy
!
clock timezone PCTime -5
clock summer-time PCTime date Apr 6 2003 2:00 Oct 26 2003 2:00
ip subnet-zero
no ip source-route
!
!
ip cef
ip inspect log drop-pkt
ip inspect name SDM_MEDIUM appfw SDM_MEDIUM
ip inspect name SDM_MEDIUM cuseeme
ip inspect name SDM_MEDIUM dns
ip inspect name SDM_MEDIUM ftp
ip inspect name SDM_MEDIUM h323
ip inspect name SDM_MEDIUM https
ip inspect name SDM_MEDIUM icmp
ip inspect name SDM_MEDIUM imap reset
ip inspect name SDM_MEDIUM pop3 reset
ip inspect name SDM_MEDIUM rcmd
ip inspect name SDM_MEDIUM realaudio
ip inspect name SDM_MEDIUM rtsp
ip inspect name SDM_MEDIUM esmtp
ip inspect name SDM_MEDIUM sqlnet
ip inspect name SDM_MEDIUM streamworks
ip inspect name SDM_MEDIUM tftp
ip inspect name SDM_MEDIUM tcp
ip inspect name SDM_MEDIUM udp
ip inspect name SDM_MEDIUM vdolive
ip inspect name SDM_MEDIUM sip
ip inspect name SDM_MEDIUM sip-tls
ip tcp synwait-time 10
no ip bootp server
ip domain name wtbhome.net
ip name-server 71.242.0.12
ip ssh time-out 60
ip ssh authentication-retries 2
!
appfw policy-name SDM_MEDIUM
application im aol
service default action allow alarm
service text-chat action allow alarm
server permit name login.oscar.aol.com
server permit name toc.oscar.aol.com
server permit name oam-d09a.blue.aol.com
application im msn
service default action allow alarm
service text-chat action allow alarm
server permit name messenger.hotmail.com
server permit name gateway.messenger.hotmail.com
server permit name webmessenger.msn.com
application http
strict-http action allow alarm
port-misuse im action reset alarm
port-misuse p2p action reset alarm
port-misuse tunneling action allow alarm
application im yahoo
service default action allow alarm
service text-chat action allow alarm
server permit name scs.msg.yahoo.com
server permit name scsa.msg.yahoo.com
server permit name scsb.msg.yahoo.com
server permit name scsc.msg.yahoo.com
server permit name scsd.msg.yahoo.com
server permit name cs16.msg.dcn.yahoo.com
server permit name cs19.msg.dcn.yahoo.com
server permit name cs42.msg.dcn.yahoo.com
server permit name cs53.msg.dcn.yahoo.com
server permit name cs54.msg.dcn.yahoo.com
server permit name ads1.vip.scd.yahoo.com
server permit name radio1.launch.vip.dal.yahoo.com
server permit name in1.msg.vip.re2.yahoo.com
server permit name data1.my.vip.sc5.yahoo.com
server permit name address1.pim.vip.mud.yahoo.com
server permit name edit.messenger.yahoo.com
server permit name messenger.yahoo.com
server permit name http.pager.yahoo.com
server permit name privacy.yahoo.com
server permit name csa.yahoo.com
server permit name csb.yahoo.com
server permit name csc.yahoo.com
!
username tborland privilege 15 secret 5 ??????????????
!
!
!
bridge irb
!
!
!
interface FastEthernet0
!
interface FastEthernet1
!
interface FastEthernet2
!
interface FastEthernet3
!
interface FastEthernet4
description $ES_WAN$$FW_OUTSIDE$
ip address dhcp
ip access-group 101 in
no ip redirects
no ip unreachables
no ip proxy-arp
ip inspect SDM_MEDIUM out
ip nat outside
ip virtual-reassembly
ip route-cache flow
duplex auto
speed auto
no cdp enable
!
interface Dot11Radio0
no ip address
!
encryption mode ciphers tkip
!
encryption vlan 1 mode ciphers tkip
!
ssid wtbhome
vlan 1
authentication open
authentication key-management wpa
wpa-psk ascii 7 ******
!
speed basic-1.0 basic-2.0 basic-5.5 6.0 9.0 basic-11.0 12.0 18.0 24.0 36.0 48.0
54.0
station-role root
no dot11 extension aironet
no cdp enable
bridge-group 1
!
interface Dot11Radio0.1
encapsulation dot1Q 1 native
no snmp trap link-status
no cdp enable
bridge-group 1
bridge-group 1 subscriber-loop-control
bridge-group 1 block-unknown-source
no bridge-group 1 source-learning
no bridge-group 1 unicast-flooding
!
interface Vlan1
description Internal Network
no ip address
ip nat inside
ip virtual-reassembly
ip tcp adjust-mss 1452
bridge-group 1
bridge-group 1 spanning-disabled
!
interface BVI1
description Bridge to Internal Network
ip address 192.168.0.1 255.255.255.0
ip access-group 100 in
no ip redirects
no ip unreachables
no ip proxy-arp
ip nat inside
ip virtual-reassembly
ip route-cache flow
ip tcp adjust-mss 1412
!
ip classless
!
no ip http server
no ip http secure-server
ip nat inside source list 1 interface FastEthernet4 overload
!
logging trap debugging
access-list 1 remark INSIDE_IF=BVI1
access-list 1 remark SDM_ACL Category=2
access-list 1 permit 192.168.0.0 0.0.0.255
access-list 100 remark auto generated by Cisco SDM Express firewall configuration
access-list 100 remark SDM_ACL Category=1
access-list 100 deny ip host 255.255.255.255 any
access-list 100 deny ip 127.0.0.0 0.255.255.255 any
access-list 100 permit ip any any
access-list 101 remark auto generated by Cisco SDM Express firewall configuration
access-list 101 remark SDM_ACL Category=1
access-list 101 permit udp any eq bootps any eq bootpc
access-list 101 permit icmp any any echo-reply
access-list 101 permit icmp any any time-exceeded
access-list 101 permit icmp any any unreachable
access-list 101 deny ip any any
access-list 103 remark VTY Access-class list
access-list 103 remark SDM_ACL Category=1
access-list 103 permit ip 192.168.0.0 0.0.0.255 any
access-list 103 deny ip any any
no cdp run
!
control-plane
!
bridge 1 protocol ieee
bridge 1 route ip
banner login ^CAuthorized access only!
Disconnect IMMEDIATELY if you are not an authorized user!^C
!
line con 0
no modem enable
transport output telnet
line aux 0
transport output telnet
line vty 0 4
access-class 103 in
transport input telnet ssh
!
scheduler max-task-time 5000
scheduler allocate 4000 1000
scheduler interval 500
end

2. High Security Policy on Application Traffic

version 12.4
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Router
!
boot-start-marker
boot-end-marker
!
logging buffered 51200 warnings
enable secret 5 ???????????????????????
!
aaa new-model
!
!
aaa authentication login default local
aaa authorization exec default local
!
aaa session-id common
!
resource policy
!
clock timezone PST -8
ip cef
!
!
no ip dhcp use vrf connected
ip dhcp excluded-address 10.10.10.1 10.10.10.10
!
ip dhcp pool sdm-pool
import all
network 10.10.10.0 255.255.255.0
default-router 10.10.10.1
dns-server 208.67.222.222 208.67.220.220
!
!
no ip domain lookup
ip domain name yourdomain.com
ip name-server 208.67.222.222
ip name-server 208.67.220.220
ip inspect log drop-pkt
ip inspect name SDM_HIGH appfw SDM_HIGH
ip inspect name SDM_HIGH icmp
ip inspect name SDM_HIGH dns
ip inspect name SDM_HIGH esmtp
ip inspect name SDM_HIGH https
ip inspect name SDM_HIGH imap reset
ip inspect name SDM_HIGH pop3 reset
ip inspect name SDM_HIGH tcp
ip inspect name SDM_HIGH udp
!
appfw policy-name SDM_HIGH
application im aol
service default action reset alarm
service text-chat action reset alarm
server deny name login.oscar.aol.com
server deny name toc.oscar.aol.com
server deny name oam-d09a.blue.aol.com
audit-trail on
application im msn
service default action reset alarm
service text-chat action reset alarm
server deny name messenger.hotmail.com
server deny name gateway.messenger.hotmail.com
server deny name webmessenger.msn.com
audit-trail on
application http
strict-http action reset alarm
port-misuse im action
port-misuse p2p action reset alarm
port-misuse tunneling action reset alarm
application im yahoo
service default action reset alarm
service text-chat action reset alarm
server deny name scs.msg.yahoo.com
server deny name scsa.msg.yahoo.com
server deny name scsb.msg.yahoo.com
server deny name scsc.msg.yahoo.com
server deny name scsd.msg.yahoo.com
server deny name cs16.msg.dcn.yahoo.com
server deny name cs19.msg.dcn.yahoo.com
server deny name cs42.msg.dcn.yahoo.com
server deny name cs53.msg.dcn.yahoo.com
server deny name cs54.msg.dcn.yahoo.com
server deny name ads1.vip.scd.yahoo.com
server deny name radio1.launch.vip.dal.yahoo.com
server deny name in1.msg.vip.re2.yahoo.com
server deny name data1.my.vip.sc5.yahoo.com
server deny name address1.pim.vip.mud.yahoo.com
server deny name edit.messenger.yahoo.com
server deny name messenger.yahoo.com
server deny name http.pager.yahoo.com
server deny name privacy.yahoo.com
server deny na
server deny name csb.yahoo.com
server deny name csc.yahoo.com
audit-trail on
!
!
crypto pki trustpoint TP-self-signed-2642721116
enrollment selfsigned
subject-name cn=IOS-Self-Signed-Certificate-2642721116
revocation-check none
rsakeypair TP-self-signed-2642721116
!
!
crypto pki certificate chain TP-self-signed-2642721116
certificate self-signed 01
3082024D 308201B6 A0030201 02020101 300D0609 2A864886 F70D0101 04050030
31312F30 2D060355 04031326 494F532D 53656C66 2D536967 6E65642D 43657274
69666963 6174652D 32363432 37323131 3136301E 170D3038 30313136 30353033
34325A17 0D323030 31303130 30303030 305A3031 312F302D 06035504 03132649
4F532D53 656C662D 5369676E 65642D43 65727469 66696361 74652D32 36343237
32313131 3630819F 300D0609 2A864886 F70D0101 01050003 818D0030 81890281
8100CB9E 16476447 E416F6C1 A994AB08 1525CF8E FA38C653 49ED2B44 34A66AC9
4D9C2677 71756644 0D54DBB1 11C224E5 4D17EC67 2148384A FE15B177 3C8D3710
4338044F 6672B697 9FEBC408 EA552F2A 6B2C7035 2E38B6F8 55E09757 0AC5A2
163FFA91 C26D8443 3EFBDFD1 CE078C9C 350AE5E5 EE866021 491C4362 8476AD3D
0E930203 010001A3 75307330 0F060355 1D130101 FF040530 030101FF 30200603
551D1104 19301782 15526F75 7465722E 796F7572 646F6D61 696E2E63 6F6D301F
0603551D 23041830 16801444 9A67C06B 63BCAF40 5D467966 AA658D22 F6353430
1D060355 1D0E0416 0414449A 67C06B63 BCAF405D 467966AA 658D22F6 3534300D
06092A86 4886F70D 01010405 00038181 005D6986 D31370A4 A327EB4B FF7ED748
25C11602 76C2A0B7 A0A1D670 7DF73001 BFAEEFF9 E6C4BE6F EB9BF6DC 1FD7D8
9B571B6E C4A4307C B1A03F91 92EF08BF B249D567 1A46D51D 3405862C A88BFCC7
AD9B755A B2BB1298 271B6952 7A08CD61 F89A31B6 A2DB9C6F 62B00F6D 7089A7FB
44D7D866 D527960F 7A138B26 92252C4B D4
quit
username tborland privilege 15 secret 5 ??????????????
!
!
!
bridge irb
!
!
!
interface FastEthernet0
!
interface FastEthernet1
!
interface FastEthernet2
!
interface FastEthernet3
!
interface FastEthernet4
description $ETH-WAN$
no ip address
duplex auto
speed auto
pppoe enable
pppoe-client dial-pool-number 1
!
interface Vlan1
description $ETH-SW-LAUNCH$$INTF-INFO-HWIC 4ESW$
no ip address
ip tcp adjust-mss 1452
bridge-group 1
!
interface Dialer0
description $FW_OUTSIDE$
ip address negotiated
ip access-group 101 in
ip mtu 1492
ip inspect SDM_HIGH out
encapsulation ppp
dialer pool 1
dialer-group 1
ppp authentication chap pap callin
ppp chap hostname [my dsl account]
ppp chap password 0 [password]
ppp pap sent-username [my_dsl_account] password 0 [password]
ppp ipcp dns request
ppp ipcp route default
ppp ipcp address accept
!
interface BVI1
description $ETH-SW-LAUNCH$$INTF-INFO-HWIC 4ESW$
ip address 10.10.10.1 255.255.255.0
ip access-group 100 in
ip tcp adjust-mss 1452
!
!
!
no ip http server
no ip http secure-server
ip nat inside source list 1 interface Dialer0 overload
!
access-list 1 permit 10.10.10.0 0.0.0.255
access-list 100 remark auto generated by SDM firewall configuration
access-list 100 remark SDM_ACL Category=1
access-list 100 deny ip host 255.255.255.255 any
access-list 100 deny ip 127.0.0.0 0.255.255.255 any
access-list 100 permit ip any any
access-list 101 remark auto generated by SDM firewall configuration
access-list 101 remark SDM_ACL Category=1
access-list 101 permit icmp any any echo-reply
access-list 101 permit icmp any any time-exceeded
access-list 101 permit icmp any any unreachable
access-list 101 deny ip any any log
dialer-list 1 protocol ip permit
!
!
!
!
control-plane
!
bridge 1 protocol ieee
bridge 1 route ip
banner login ^CAuthorized access only!
Disconnect IMMEDIATELY if you are not an authorized user!^C
!
line con 0
no modem enable
line aux 0
line vty 0 4
access-class 1 in
transport input ssh
!
scheduler max-task-time 5000
end

Some discussion
/forum/remark,13205912?hilite=801+woes
»801 ISDN access list woes

feedback form

by aryoba
last modified: 2008-05-20 09:49:43

Extracted from following thread:
»[HELP] IOS IPS -- Is the performance hit worth it?

Note:
To run this configuration, your router needs to run IOS image that has IPSec/IDS feature and have the signature file on its flash memory. Check out the following FAQ for more info.

»Cisco Forum FAQ »Protect my network! How do I do that using Cisco IOS?



feedback form

by aryoba
last modified: 2007-07-11 11:09:37

Note:

* Router needs to run 12.4 IOS image



feedback form

by aryoba
last modified: 2008-02-10 08:12:51

A solution which uses the router to filter Internet access (web traffic), allowing what is defined to go through and deny all others.

Option 1: Using CBAC feature

This "work around" is the use of Cisco's Web Filtering functionality which goes hand in hand with the Websense products. This FAQ will utilise the current functionality of the Websense solution without a server by deviating from the original design of this suite of technologies by Cisco.

Note that this is only supported in IOS that have the CBAC functionality.

First off, create an ACL which will be used in the Java filter statement that allows everything through which will not trigger the Java applet scanner which can be CPU intensive. If not, degraded performance can occur.


Define the IP INSPECT statements as below and then add what URLs are allowed to be accessed such as www.google.com and www.froogle.com in the example below:


The statement "ip urlfilter exclusive-domain www.xxxx.com" adds a domain name to or from the exclusive domain list so that the firewall does not have to send look-up requests to the Websense server. So, regardless of the Websense server being available or not, which in this case does not exist, the router will allow all HTTP requests to the above domains through.

There is a setting which is defined by the statement "ip urlfilter allow-mode on/off" where if the router can't talk to the Websense server, it will allow web traffic through or deny it depending on this setting. There is no Websense server defined at all but what we will do is turn off the allow-mode so all traffic will be denied bar the ones defined in the exclusive-domain statement.


Now the configuration has been setup, it then has to be applied to the interface like a normal ip inspect statement, for example:


or


Option 2: Using QoS CBWFQ feature

Using the same previous situation, the permitted web sites are only www.google.com and www.froogle.com; while traffic to other sites are blocked. This time the filtering technique is utilising CBWFQ which is also applied to the WAN interface.


CBWFQ (Class Based Weighted Fair Queue) is Cisco QoS (Quality of Service) feature that can be used to shape or to drop certain traffic. In this sample configuration, outbound traffic to www.google.com, to www.froogle.com, and to ISP DNS servers are set to guarantee 20% bandwidth during congestion. Other traffic will be dropped even when there is no congestion.

Let's review another illustration. Some organizations prevent their employee to access public social sites such as www.myspace.com and adult (porn) sites such as www.playboy.com; while still permit access to other Internet sites. Using the CBWFQ, following is blocked-access sample configuration.


More illustration on CBWFQ technique to restrict/maintain website access
»[Config] QoS with CBWFQ to prioritize a website

Option 3: Using ACL IP Address-Based

The downside of the two previous sample configurations is that your router may not support such feature. A good side is that most router support access block by IP addresses or subnets. Following is illustration on how to block access by the site's IP addresses, which the filter is applied to the LAN interface.

Let's revisit the www.myspace.com access block. Using DNS A record and WHOIS checks, it is revealed that currently myspace.com subnet is 216.178.32.0/20 (from 216.178.32.0 to 216.178.47.255). Following is the sample configuration of block access to myspace.com based on its IP addresses.


Side Note:

You can use following site for public DNS A record and WHOIS checking
http://www.iptools.com/

Note that this block access method only works when myspace.com still occupies the 216.178.32.0/20 subnet. It was known that originally myspace.com did not occupy this subnet. When the blocked site IP addresses are moved to different subnet, then there will be a need to adjust the blocked IP subnet to the new one. This adjustment is not needed when one of the two previous options is deployed.

This FAQ was inspired by the following post:
»How to Configure Internet Access restrictions ?

feedback form

by Covenant edited by aryoba
last modified: 2007-12-26 13:05:27

Suggested prerequisite reading
»Cisco Forum FAQ »Setting Up Private Site-To-Site Connections

Introduction

Setting up site-to-site IPSec VPN connection in general involves two phases. Phase 1 is called ISAKMP SA (Security Association) establishment and Phase 2 is called IPSec SA establishment.

Phase 1

In general, Phase 1 deals with confirmation among sites that are about to establish secure connection across unsecure network. This process is to verify that each site is authorized to establish such connection. Following is further description.

Phase 1 is to establish the ISAKMP key matching with remote site. One popular technique of this ISAKMP key matching is to use preshared key. This key is basically a string (combination of alphabets, numbers, and characters) that both sites agree to use. The key is then stored (and encrypted) within each VPN device configuration.

Phase 1 in IPSec VPN connection establishment is also involving the remote VPN device IP address (peer). A popular technique is to specifically set the remote peer IP address (for security purposes); known as static configuration. With this specific static configuration, both preshared key and remote IP address are statically configured into the VPN device.

During the Phase 1 VPN tunnel establishment using the static configuration of both preshared key and remote IP address, the two VPN peer IP addresses (the local and the remote) must match. If the two VPN peer IP addresses match, then the next step is to match the preshared key between the two VPN devices.

This preshared key matching process is done within an encapsulated secure (encrypted) tunnel. The encapsulation type and method used is the encryption specified for the Phase 1. In other word, Phase 1 VPN tunnel establishment in this case involves matching process of three factors where all the three are statically configured into both VPN devices. If there is a change needed to the either one of the three, manual adjustment is needed.

The three factors are VPN peer IP addresses, preshared key, and encryption type and method. In this specific example, those three factors are the key of how Phase 1 process take place to verify security association establishment between sites that are about to setup secure connection over untrusted network.

Phase 2

Once Phase 1 is passed successfully, then the setup process moves to the Phase 2. In general, Phase 2 deals with traffic management of the actual data communication between sites. There will be mechanism to determine which data goes where, encrypted or not.

In Cisco security device, one mechanism factor is to use access list. An access list is used to specify or regulate which data (source and destination IP addresses or subnets) need to be encrypted or decrypted (going through the VPN tunnel).

Similar to the Phase 1, there is also specific remote VPN peer IP addresses and IPSec VPN tunnel type and method only for the Phase 2. All the access list, remote VPN peer IP addresses, and the Phase 2 IPSec VPN tunnel type and method are statically configured into both VPN devices. The actual data passing (that are encrypted before leaving local VPN device to go to the remote VPN device; and are decrypted when arriving at local VPN device from the remote VPN device) are encapsulated within the Phase 2 IPSec VPN tunnel.

In other word, the access list, VPN peer IP addresses, and IPSec VPN tunnel type and method are the key to establish the Phase 2. Once Phase 2 is established, the actual data between sites will be passing.

Between Phase 1 and Phase 2

Note that only the Phase 2 involves the IPSec protocol, either ESP (Protocol 50) or AH (Protocol 51). Both Phase 1 (ISAKMP) and Phase 2 (IPSec) use specific encryption type (i.e. AES, 3DES, DES) and hash (MD5 or SHA). Specifically for Phase 1, there is the Diffie-Hellman group type (Group 1, 2, or 5) and the ISAKMP SA (Security Association) timeout or lifetime.

Cisco Configuration Guide
An Introduction to IP Security (IPSec) Encryption
Virtual Private Networks with the Cisco PIX Firewall - Introduction and Implementation

Illustration

Let's review the following PIX IPSec VPN tunnel configuration


To understand the complete picture, please review the PIX-to-PIX IPSec Fully Meshed Sample Configuration.

Side Note:
Further understanding regarding each PIX command and technology behind it, check out the following Cisco link:
Cisco PIX Firewall Command Reference Version 6.3

Note that from VPN connection perspective, the actual data can only be passing between two sites when followings are met (in addition of other basic interconnectivity requirement)

* Phase 1 is established: matching VPN peer IP address, preshared key, Phase 1 encryption type and method
* Phase 2 is established: matching VPN peer IP address, access list, Phase 2 IPSec type and method
* Proper IP Routing is in place: either by static routes or by dynamic routing protocol

In other words, configuration between two VPN devices must match.

Sample Configurations

Following is sample configuration of site-to-site IPSec VPN tunnel between two sites. As to full mesh (or partially mesh) site-to-site VPN involving three or more sites, it is basically similar setup as the single site-to-site VPN between two sites. You just need to setup the tunnel one by one; between 1st and 2nd sites, between 1st and 3rd sites, between 2nd and 3rd sites, and so on.

Specifically in setting up IPSec tunnel on Cisco router, PIX, or ASA in hub and spoke, partially mesh, or fully mesh setup that involve three or more sites; you need to use different sequence number of "crypto map" command for each remote VPN IP address and specific access list that regulate the encrypted traffic. The PIX-to-PIX sample configuration illustrates that.

PIX to PIX
Configuring PIX to PIX to PIX IPSec Fully Meshed

Router to Router

1. Basic Configuration
Configuring Router-to-Router IPSec Using AES Encryption
Configuring IPSec Between Three Routers Using Split Tunneling
Configuring IPSec Router-to-Router Hub and Spoke
Configuring IPSec Router-to-Router Hub and Spoke with Communication Between the Spokes
Configuring IPSec Router-to-Router Fully Meshed

2. Extended Configuration
Configuring an IPSec Tunnel through a Firewall with NAT
Configuring a Router IPsec Tunnel Private-to-Private Network with NAT and a Static
Configuring an IPSec Tunnel Between Routers with Duplicate LAN Subnets
Configuring IPSec Router-to-Router, Pre-shared, NAT Overload Between a Private and a Public Network
Configuring a Router-to-Router LAN-to-LAN Tunnel with a Router Initiating IKE Aggressive Mode
Configuring an IPsec Router Dynamic LAN-to-LAN Peer and VPN Clients

Router to VPN 3000 Concentrator
Configuring the Cisco VPN 3000 Concentrator to a Cisco Router
EZ VPN

PIX to Router
http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a0080094498.shtml

PIX to VPN 3000 Concentrator
http://www.cisco.com/en/US/products/hw/vpndevc/ps2284/products_configuration_example09186a00800949d2.shtml

PIX to Checkpoint 4.1 Firewall
http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a008009420f.shtml

PIX to Checkpoint NG Firewall
http://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a00800ef796.shtml

PIX to Juniper Netscreen Firewall
http://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a00801c4445.shtml

PIX to Sonicwall
http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a008052c9d4.shtml

PIX to Zywall
»Cisco Forum FAQ »How do I configure a Zywall/Pix ipsec VPN

Various Cisco Devices to Microsoft Windows server
http://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a00800b12b5.shtml

Some discussions
»[Config] Configuring More Than 1 VPN Tunnel (871w)

Basic Troubleshooting

1. Phase 2 (IPSec - the actual data passing)

* Make sure the data source and destination IP addresses or subnets match the regulating access list
* Check the data passing process between the two sites. In Cisco equipment, you can issue the show crypto ipsec sa command or feature which will show the SA (Security Association) between encrypted traffic (outgoing data) and decrypted traffic (incoming data)

2. Phase 1 (ISAKMP - the key)

* Assuming you use preshared key, make sure the remote VPN peer IP address and key match between two VPN device configuration
* Check the Phase 1 VPN tunnel up/down status between two sites. In Cisco equipment, you can issue the show crypto isakmp sa command or feature which will show the up/down tunnel status between local VPN peer IP address and remote VPN peer IP address.
* Issue simple connection test to the remote site (the remote VPN peer IP address) such as ICMP ping and traceroute (whenever possible)
* Reboot one or both VPN devices sometime might solve VPN connectivity issue

Further Reading:
VPN Tunnel To Support Non-IP traffic and/or Dynamic Routing Protocols: GRE over IPSec
»Cisco Forum FAQ »Private Routing over VPN: GRE over IP Sec

feedback form

by aryoba
last modified: 2008-07-07 13:58:15

The network layout that this configuration works for is
192.168.0.0 /24 -> Zywall 2x -> Speedstream 5100(PPOE)->internet ->Cisco 1720 -> x.x.x.192 /26 public ip pool -> Pix 501 -> 192.168.1.0 /24
The outside interface of the Pix is x.x.x.194

Pix config

MYCOFW# write t
PIX Version 6.1(2)
nameif ethernet0 outside security0
nameif ethernet1 inside security100
hostname MYCOFW
domain-name MYCOMPANY.com
access-list To-Internet permit ip 192.168.1.0 255.255.255.0 any
access-list To-Internet permit ip 192.168.2.0 255.255.255.0 any
access-list To-Internet permit icmp any any
access-list From-Internet permit tcp any host x.x.x.196 eq smtp
access-list From-Internet permit icmp any x.x.x.192 255.255.255.192 echo
access-list From-Internet permit icmp any x.x.x.192 255.255.255.192 echo-reply
access-list From-Internet permit icmp any x.x.x.192 255.255.255.192 unreachable
access-list From-Internet permit icmp any x.x.x.192 255.255.255.192 time-exceeded
access-list NoNAT permit ip 192.168.1.0 255.255.255.0 192.168.2.0 255.255.255.0
access-list NoNAT permit ip 192.168.1.0 255.255.255.0 192.168.0.0 255.255.255.0
access-list to-internet permit icmp any any
interface ethernet0 10baset
interface ethernet1 10full
mtu outside 1500
mtu inside 1500
ip address outside x.x.x.194 255.255.255.192
ip address inside 192.168.1.25 255.255.255.0
ip local pool MYCOippool 192.168.2.1-192.168.2.254
global (outside) 1 x.x.x.200-x.x.x.250 netmask 255.255.255.192
global (outside) 1 x.x.x.251
nat (inside) 0 access-list NoNAT
nat (inside) 1 192.168.1.0 255.255.255.0 0 0
access-group From-Internet in interface outside
access-group To-Internet in interface inside
route outside 0.0.0.0 0.0.0.0 x.x.x.193 1
http 192.168.1.0 255.255.255.0 inside
sysopt connection permit-ipsec
sysopt connection permit-pptp
no sysopt route dnat
crypto ipsec transform-set MyCOTransf esp-3des esp-md5-hmac
crypto dynamic-map MYCOdynmap 10 set transform-set MYCOTransf
crypto map MYCOmap 10 ipsec-isakmp dynamic MYCOdynmap
crypto map MYCOmap client configuration address initiate
crypto map MYCOmap client configuration address respond
crypto map MYCOmap interface outside
isakmp enable outside
isakmp key ******** address 0.0.0.0 netmask 0.0.0.0 no-xauth no-config-mode
isakmp identity address
isakmp client configuration address-pool local MYCOippool outside
isakmp policy 10 authentication pre-share
isakmp policy 10 encryption 3des
isakmp policy 10 hash md5
isakmp policy 10 group 2
isakmp policy 10 lifetime 28800
vpngroup MYCOvpn address-pool NONATippool
vpngroup MYCOvpn dns-server 205.171.3.65
vpngroup MYCOvpn wins-server 192.168.1.1
vpngroup MYCOvpn default-domain MYCOMPANY.com
vpngroup MYCOvpn idle-time 1800
vpngroup MYCOvpn password ********
vpngroup MYCO address-pool NONATippool
vpngroup MYCO dns-server 192.168.1.1 205.171.3.65
vpngroup MYCO wins-server 192.168.1.1
vpngroup MYCO default-domain MYCO.com
vpngroup MYCO idle-time 1800
vpngroup MYCO password ********
vpdn group 1 accept dialin pptp
vpdn group 1 ppp authentication pap
vpdn group 1 ppp authentication chap
vpdn group 1 ppp authentication mschap
vpdn group 1 client configuration address local NONATippool
vpdn group 1 pptp echo 60
vpdn group 1 client authentication local
vpdn username xxxx password xxxx
vpdn username yyyy password yyyyy
vpdn username zzzz password zzzzz
vpdn enable outside

Zywall Config:

Menu 27.1.1 - IPSec Setup

Index #= 1 Name= Work
Active= Yes Keep Alive= Yes Nat Traversal= No
Local ID type= IP Content=
My IP Addr= 0.0.0.0
Peer ID type= IP Content= x.x.x.194
Secure Gateway Address= x.x.x.194
Protocol= 17
Local: Addr Type= SUBNET
IP Addr Start= 192.168.0.0 End/Subnet Mask= 255.255.255.0
Port Start= 0 End= N/A
Remote: Addr Type= SUBNET
IP Addr Start= 192.168.1.0 End/Subnet Mask= 255.255.255.0
Port Start= 0 End= N/A
Enable Replay Detection= Yes
Key Management= IKE

Menu 27.1.1.1 - IKE Setup

Phase 1
Negotiation Mode= Main
PSK= ********
Encryption Algorithm= 3DES
Authentication Algorithm= MD5
SA Life Time (Seconds)= 28800
Key Group= DH2

Phase 2
Active Protocol= ESP
Encryption Algorithm= 3DES
Authentication Algorithm= MD5
SA Life Time (Seconds)= 28800
Encapsulation= Tunnel
Perfect Forward Secrecy (PFS)= None

In addition I had to enable 2 firewall rules on the Zywall Wan/WanZywall interface.
1) Source address (x.x.x.192 255.255.255.192) Destination (Any) forward Any Tcp Any Udp

2) source address (Any) Destination (Any) forward (ike,gre,ah,esp) I also include icmp & auth, though I don't think these are necessary for the vpn, they help with dslr line monitoring & my mail server.

This is a thumbnail of the image, click to enlarge.


feedback form

by TerryMiller edited by aryoba
last modified: 2006-09-12 05:57:47

PIX passing IPSec tunnel
Configuring an IPSec Tunnel through a PIX Firewall with NAT

GRE passing over PIX-to-PIX IPSec tunnel to support OSPF
Configuring a GRE Tunnel over IPSec with OSPF

IPSec tunnel passthrough on NAT/PAT Device and Utilize Single Public IP Address For Both Internet and IPSec Tunnel

1. Router as the NAT/PAT Device
IOS Router to Pass a LAN-to-LAN IPSec Tunnel via PAT

2. PIX Firewall as the NAT/PAT Device
»www.cisco.com/en/US/tech/tk583/t···6e.shtml

feedback form

by aryoba
last modified: 2008-01-23 16:09:19

Suggested prerequisite reading:
»Cisco Forum FAQ »Setting Up Private Site-To-Site Connections
»Cisco Forum FAQ »Between GRE/IPSEC and IPSEC VPN tunnels

When you need to broadcast private routing (dynamic routing protocols) over VPN, then in general you need to run GRE over IP Sec. Followings are the sample configurations.

Running OSPF

Configuring a GRE Tunnel over IPSec with OSPF

Running EIGRP

GRE over IPSec with EIGRP to Route Through a Hub and Multiple Remote Sites

IPX Routing over GRE/IPSec

Configuring GRE and IPSec with IPX Routing
Configuring IPSec with EIGRP and IPX Using GRE Tunneling

Note:
The previous sample configurations assume both the GRE and IPSec VPN terminate at a router. When somehow the router IOS image feature only supports GRE tunnel and there will be a PIX Firewall in front of the router to establish the IPSec tunnel, then you can check out the following FAQ for illustrations.

»Cisco Forum FAQ »PAT/NAT Router/PIX passing through VPN tunnel

For full mesh site-to-site VPN with the above GRE over IPSec approach involving three sites or more, it is basically similar setup as the single site-to-site VPN between two sites. You just need to setup the tunnel one by one; between 1st and 2nd sites, between 1st and 3rd sites, between 2nd and 3rd sites, and so on.

DMVPN

When Cisco routers act as the VPN device at all sites, it is simpler and scalable to run DMVPN between routers instead the previous GRE over IPSec approach. With DMVPN, there will be no need to manually setup each tunnel for each connection between two sites. DMVPN will be "dynamically" setting up necessary tunnels.

Should you decide to run DMVPN, verify your router IOS image version support it. IOS image version with Advanced Enterprise (or probably Advanced IP Services) feature should support DMVPN.

Check out following links for more info on DMVPN.

Dynamic Multipoint IPsec VPNs (Using Multipoint GRE/NHRP to Scale IPsec VPNs)
Configuring DMVPN Spoke Router in Full Mesh IPsec VPN Using SDM
Configuring Dynamic Multipoint VPN Using GRE Over IPsec With OSPF, NAT, and Cisco IOS Firewall

New Feature on ASA or PIX Firewall running OS version 7.x or later

With new OS version, it is no longer requirement to encapsulate OSPF into GRE tunnel in order to pass it through IPSec VPN tunnel. By running OS version 7.x or later, ASA or PIX Firewall is now able to pass OSPF through IPSec VPN tunnel just like pass through GRE or any IP traffic. Check out the following link for sample configuration.

PIX/ASA 7.x and later: VPN/IPsec with OSPF Configuration Example

feedback form

by aryoba
last modified: 2008-07-14 11:11:33