DNS "recursion not available" using a Cisco AnyConnect VPN connection
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by codeape
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Published on 2010-01-20T17:56:42Z
Indexed on
2010/04/01
11:03 UTC
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Does anyone have experience with configuring Cisco AnyConnect VPN? We have a problem with client DNS name resolution when connected over VPN.
To me, it looks as if the Cisco AnyConnect VPN client intercepts DNS queries from the clients.
- Can someone confirm that the AnyConnect VPN client in fact does this (intercepts DNS traffic)?
- Where is this configured on the VPN server?
EDIT:
Here's how the routing table changes when I connect to the VPN:
[~]
$ diff -u /tmp/route_normal /tmp/route_vpn
--- /tmp/route_normal 2010-01-20 19:23:47.000000000 +0100
+++ /tmp/route_vpn 2010-01-20 19:24:46.000000000 +0100
@@ -1,6 +1,10 @@
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
+xxx.xxx.xx.xx.i 10.0.0.1 255.255.255.255 UGH 0 0 0 ath0
172.16.53.0 * 255.255.255.0 U 0 0 0 vmnet1
10.0.0.0 * 255.255.255.0 U 0 0 0 ath0
+172.17.20.0 * 255.255.255.0 U 0 0 0 cscotun
0
+192.168.111.0 172.17.20.212 255.255.255.0 UG 0 0 0 cscotun
0
172.16.140.0 * 255.255.255.0 U 0 0 0 vmnet8
+172.16.0.0 172.17.20.212 255.255.0.0 UG 0 0 0 cscotun
0
default 10.0.0.1 0.0.0.0 UG 0 0 0 ath0
EDIT 2:
The IT guy has done "something" on the VPN endpoint. Now I get "recursion not available" when doing nslookup
. The DNS servers have recursion enabled. So it must be the Cisco VPN DNS interception messing this up.
ubuntu@domU-12-31-39-00-ED-14:~$ /opt/cisco/vpn/bin/vpn connect xxx.xxxxxx.xx
...
>> Please enter your username and password
...
>> notice: Establishing VPN...
>> state: Connected
>> notice: VPN session established to ...
ubuntu@domU-12-31-39-00-ED-14:~$ nslookup www.vg.no
;; Got recursion not available from ..., trying next server
;; Got recursion not available from ..., trying next server
;; Got recursion not available from ..., trying next server
;; Got recursion not available from ..., trying next server
Server: 172.16.0.23
Address: 172.16.0.23#53
** server can't find www.vg.no.compute-1.internal: REFUSED
ubuntu@domU-12-31-39-00-ED-14:~$ ping 195.88.55.16
PING 195.88.55.16 (195.88.55.16) 56(84) bytes of data.
64 bytes from 195.88.55.16: icmp_seq=1 ttl=240 time=110 ms
64 bytes from 195.88.55.16: icmp_seq=2 ttl=240 time=111 ms
64 bytes from 195.88.55.16: icmp_seq=3 ttl=240 time=109 ms
^C
--- 195.88.55.16 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2017ms
rtt min/avg/max/mdev = 109.953/110.379/111.075/0.496 ms
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