CCIE Pursuit Blog

November 26, 2007

LFU 9: Beware The Implied OSPF Process!!!

I ran into an interesting issue on the Internetwork Expert Volume II lab 2 this weekend.  I noticed that I had a rogue OSPF process showing up on one of my switches (3560).  I had configured OSPF process 100, but not OSPF process 17 (17 wasthe area that the sw1 OSPF interfaces were in):

sw1#sh ip proto sum
Index Process Name
0     connected
1     static
2     ospf 100
3     rip
4     ospf 17   <-where did this come from?
*** IP Routing is NSF aware ***

sw1#sh ip proto | b ospf
Routing Protocol is “ospf 100”
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Router ID 150.1.7.7
  It is an autonomous system boundary router
  Redistributing External Routes from,
    rip, includes subnets in redistribution
  Number of areas in this router is 1. 1 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    132.1.17.7 0.0.0.0 area 17
  Routing Information Sources:
    Gateway         Distance      Last Update
    150.1.3.3            110      00:18:43
    150.1.2.2            110      00:18:43
    150.1.1.1            110      01:44:44
    150.1.7.7            110      01:44:44
  Distance: (default is 110)

There was no other OSPF process configure.  I thought that maybe I accidentally configured “router os 17” at some point, but when I looked at the configuration all that was there was OSPF 100.  I thought that there must be some bug in the switch IOS.  The phantom OSPF process was showing up in the “show ip protocol summary” output but not in the “show ip protocol” output.  I reloaded the switch just in case.

That didn’t solve the issue.  I looked through the configuration and found the issue…under the RIP process!  This solves the mystery of the “ospf 17”:

sw1#sh run | b router rip
router rip
 version 2
 redistribute ospf 17 metric 1   <-whoops!  
 offset-list EVEN in 16 Vlan783
 network 150.1.0.0
 network 204.12.1.0
 no auto-summary

This explains my route redistribution issue as well!  I must have typed in the area number instead of the correct OSPF process (100) when redistributing OSPF into RIP.  This is the type of fat-finger issue that can make you fail your lab.  I banged my head on my desk and corrected the process ID.

sw1#sh run | b router rip
router rip
 version 2
 redistribute ospf 100 metric 1    
 offset-list EVEN in 16 Vlan783
 network 150.1.0.0
 network 204.12.1.0
 no auto-summary

Strange, IOS must assume the existence (or imminent existence) of a routing process if you reference it in a redistribution statement.  What’s even stranger is that even after I removed (changed) the reference…it still showed up:

sw1#sh ip proto sum
Index Process Name
0     connected
1     static
2     ospf 100
3     rip
4     ospf 17
*** IP Routing is NSF aware ***

WTF?  Was I being haunted by an undead OSPF process?  I verified that there was nothing left in the configuration that referred to OSPF process 17:

sw1#sh run | i 17
 ip address 132.1.17.7 255.255.255.0
interface FastEthernet0/17
 area 17 authentication
 network 132.1.17.7 0.0.0.0 area 17

So the process was not configured and there was no longer any reference to it, so why was it still showing up?

sw1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
sw1(config)#no router ospf 17
sw1(config)#
sw1(config)#do sh ip proto sum
Index Process Name
0     connected
1     static
2     ospf 100
3     rip
*** IP Routing is NSF aware ***

Lesson learned: if you reference an OSPD process that does not exist (in RIP at least) then the router assumes that this process is actually running.  You’ll need to explicitly remove the process (“no router ospf x”) in order to remove it from the “show ip protocol summary” output.

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