Hi Jose,
I think that generally SUP32 isn't suitable for todays full internet
routing table. It's due to the hardware limitations (as you wrote).
When you have full routes on SUP32 you should see log output as below
%MLSCEF-SP-4-FIB_EXCEPTION_THRESHOLD: Hardware CEF entry usage is at 95%
capacity for IPv4 unicast protocol.
%CFIB-SP-7-CFIB_EXCEPTION: FIB TCAM exception, Some entries will be
software switched
I have seen similar troubles with some sites/networks weren't reachable
throught SUP720-3B (non XL) routers, but the routing and CEF table were
correct.
Regards,
Marek
On Wed, 21 Jan 2009, Jose wrote:
I was wondering if I could get some additional opinions on a case I have open
with Cisco. We have recently started turning up LDP on various links out
towards some routers that are being converted to act as PEs. The core is all
connected together and has been running LDP on those particular links for
over 8 months.
This past weekend we turned up LDP on a link to one of our remote cities and
we received sporadic complaints that some customers couldn't access any
sites/addresses if the path was via one of our P routers. If traffic was
through any other path on the network it was fine. Traceroutes to & from
this P router showed were unsuccessful even though the routing table and LFIB
all showed the correct information. Turning off LDP across this link
resolved the problem for the customers.
After opening up the TAC case and lots of troubleshooting they showed us
this:
Without LDP on:
frort04#sh ip cef exact-route 172.17.0.254 68.179.73.86
172.17.0.254 -> 68.179.73.86 : Vlan2210 (next hop 67.226.181.110)
<<<<<< the next hop is correct
With LDP on:
frort04#sh mls cef exact-route 172.17.0.254 68.179.73.86 Interface: Vl2210,
Next Hop: 224.0.0.168, Vlan: 2210, Destination Mac: 00b0.4a5e.7419 <<<<<<<<
next hop can't be a multicast IP
the CEF entry and MLS CEF entry are different, after consulting the LAN-SW
team, it is found this router had issue of overloaded routes causing mls cef
table become corrupted.
So basically we were told that because the SUP32 has a hardware limitation of
250K routes that it can hardware cef, we were getting corruption in our
tables and in turn corrupting how LDP was building its forwarding table. The
core P routers currently hold the entire internet routing tables so yes they
technically are pretty full in terms of the number of routes they can hold.
They want us to reload our router to clear the tables but they can't
guarantee that this problem won't resurface again down the road or right
away. I'm more curious if there is some kind of IOS bug we might be hitting
which I'm hoping one of you might know but they're supposed to be doing a bug
scrub as well.
Any thoughts on what we're experiencing? Should we bite the bullet and
upgrade to SUP720-3BXLs?
Thanks.
Jose
_______________________________________________
cisco-nsp mailing list [email protected]
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/
_______________________________________________
cisco-nsp mailing list [email protected]
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/
