GroupStudy.com GroupStudy.com - A virtual community of network engineers
 Home  BookStore  StudyNotes  Links  Archives  StudyRooms  HelpWanted  Discounts  Login
O/T - RIB/FIB decisions [7:128334] posted 11/27/2007
[Chronological Index] [Thread Index] [Top] [Date Prev][Date Next] [Thread Prev][Thread Next]


Hi all,

I have a 2851 router with 3 interfaces connected to different ISP's.  The
default route is pointing out ISP1.  When I SSH into the router via the IP
on the ISP2 interface, I noticed that the reply packet is being routed out
the default route.  Funny thing is, the SSH connection isn't working when I
connect to the interface on ISP2, but it is when I connect to the IP
assigned to the ISP3 interface.  In both cases, the output of 'debug ip
packet' shows that the replies are being sent out the default route's
interface (ISP1).

This router is running IOS firewall, but the ACL's aren't blocking the
traffic.  I think it might be due to the TCP SYN going to ISP3, the SYN/ACK
coming out ISP1, and my ACK going back to ISP3.  This doesn't explain why it
works with ISP2, though.

Here's a sample.  My IP is 10.1.1.1, and the router's IP on ISP2's interface
is 192.168.2.1.

3628216: *Nov 28 01:24:58.682 UTC: IP: tableid=0, s=10.1.1.1 (Vlan140),
d=192.168.2.1 (Vlan140), routed via RIB
3628217: *Nov 28 01:24:58.682 UTC: IP: s=10.1.1.1 (Vlan140), d=192.168.2.1
(Vlan140), len 184, rcvd 3
3628218: *Nov 28 01:24:58.730 UTC: IP: tableid=0, s=192.168.2.1 (local),
d=10.1.1.1 (Multilink1), routed via FIB
3628219: *Nov 28 01:24:58.730 UTC: IP: s=192.168.2.1 (local), d=10.1.1.1
(Multilink1), len 488, sending

Any ideas?



Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=128334&t=128334
--------------------------------------------------
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html