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Getting a VPN to work through a Cisco firewall

rkunkel
Level 1
Level 1

Hello all,

The problem here lies in the firewall blocking VPN traffic. Right now, as a lab, I've got the WAN port of the router set up with a xxx.xxx.xxx.158 255.255.255.252 IP address, and the LAN as a xxx.xxx.xxx.161 255.255.255.224 IP address.

When someone from the outside makes a VPN connection to the router's WAN IP address, it grabs an address from the pool, and work fine as long as the firewall is not in place.

Once the firewall is there, the traffic can't make it back in, despite the fact that the inspect CBAC is suppose to open holes in the firewall. I get log entires like:

-- Nameserver not able to get it's traffic back:

Jan 11 19:37:45.927: %SEC-6-IPACCESSLOGP: list 101 denied udp

xxx.xxx.xxx.10(53) -> xxx.xxx.xxx.182(3758), 1 packet

-- Hitting Yahoo by IP in browser. Traffic not making it back:

Jan 11 19:37:55.875: %SEC-6-IPACCESSLOGP: list 101 denied tcp

66.94.230.34(80) -> xxx.xxx.xxx.182(3759), 1 packet

Note that the "xxx.xxx.xxx.182" IP is the IP that was handed to the VPN client, but that is ACTUALLY out on the Internet.

I have the feeling that I'm missing something dumb, but I just don't know. I usually feel pretty adept at these things.

For your inspection, here are the relevant portions of the config. Also worth noting is that I've let the Cisco SDM write the access list parts of this. I've also tried it by hand, with no success.

ip inspect name DEFAULT100 cuseeme

ip inspect name DEFAULT100 ftp

ip inspect name DEFAULT100 h323

ip inspect name DEFAULT100 icmp

ip inspect name DEFAULT100 netshow

ip inspect name DEFAULT100 rcmd

ip inspect name DEFAULT100 realaudio

ip inspect name DEFAULT100 rtsp

ip inspect name DEFAULT100 esmtp

ip inspect name DEFAULT100 sqlnet

ip inspect name DEFAULT100 streamworks

ip inspect name DEFAULT100 tftp

ip inspect name DEFAULT100 tcp

ip inspect name DEFAULT100 udp

ip inspect name DEFAULT100 vdolive

interface FastEthernet0/0

description $ETH-WAN$$FW_OUTSIDE$

ip address xxx.xxx.xxx.158 255.255.255.252

ip access-group 101 in

ip inspect DEFAULT100 out

crypto map SDM_CMAP_1

interface FastEthernet0/1

description $ETH-LAN$$FW_INSIDE$

ip address xxx.xxx.xxx.161 255.255.255.224

ip access-group 100 in

ip local pool SDM_POOL_1 xxx.xxx.xxx.176 xxx.xxx.xxx.183

access-list 100 remark auto generated by SDM firewall configuration

access-list 100 remark SDM_ACL Category=1

access-list 100 deny ip xxx.xxx.xxx.156 0.0.0.3 any

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 udp host 207.244.144.10 eq domain host xxx.xxx.xxx.158

access-list 101 permit udp host 207.244.153.11 eq domain host xxx.xxx.xxx.158

access-list 101 permit ip xxx.xxx.xxx.176 0.0.0.7 any

access-list 101 remark Auto generated by SDM for NTP (123) 72.36.170.170

access-list 101 permit udp host 72.36.170.170 eq ntp host xxx.xxx.xxx.158 eq ntp

access-list 101 permit ahp any host xxx.xxx.xxx.158

access-list 101 permit esp any host xxx.xxx.xxx.158

access-list 101 permit udp any host xxx.xxx.xxx.158 eq isakmp

access-list 101 permit udp any host xxx.xxx.xxx.158 eq non500-isakmp

access-list 101 deny ip xxx.xxx.xxx.160 0.0.0.31 any

access-list 101 permit icmp any host xxx.xxx.xxx.158 echo-reply

access-list 101 permit icmp any host xxx.xxx.xxx.158 time-exceeded

access-list 101 permit icmp any host xxx.xxx.xxx.158 unreachable

access-list 101 deny ip 10.0.0.0 0.255.255.255 any

access-list 101 deny ip 172.16.0.0 0.15.255.255 any

access-list 101 deny ip 192.168.0.0 0.0.255.255 any

access-list 101 deny ip 127.0.0.0 0.255.255.255 any

access-list 101 deny ip host 255.255.255.255 any

access-list 101 deny ip host 0.0.0.0 any

access-list 101 deny ip any any log

Thanks much!

1 Reply 1

aacole
Level 5
Level 5

What IOS version is in use here? In earlier versions (not sure when this changed) you also had to allow the pool address range in through your outside ACL.

Can you connect to a loopback address on the router, or to any addresses on the inside?

Does the IPSec tunnel come up? Have a look at show crypto isakmp sa and sh crypto ipsec sa.

I have an example somewhere of a client to IOS router with CBAC, if you need it I'll locate it and post up here.