Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

BGP default goes disappeared sometime

This is an ADSL atm network using a 2811 router.

My atm port is, edge router is

1. Every once a while the B* [20/0] via, 6d20h default route would go disappeared, so BGP would change to Active.

2. show inteface bri said, atm 0/0 was up/up

3. I connected to the router through the back door, found out, the atm 0/0 port is not pingable.

4. To resolve the issue, I would need a shut/no shut on the atm 0/0, BGP would be reestablish, and it would work for 5-15 days.

Here is my normal routing table

C is directly connected, FastEthernet0/0

C is directly connected, Loopback0

C is directly connected, ATM0/0/0

B [200/0] via, 6d20h, Null0

C is directly connected, GigabitEthernet1/0

B* [20/0] via, 6d20h

=====show log when default route disappear==

Oct 6 11:01:36.330 CDT: %PIM-5-DRCHG: DR change from neighbor to 10.152

.254.2 on interface ATM0/0/0

Oct 6 11:01:45.219 CDT: %LINK-3-UPDOWN: Interface ATM0/0/0, changed state to do


Oct 6 11:01:46.219 CDT: %LINEPROTO-5-UPDOWN: Line protocol on Interface ATM0/0/

0, changed state to down

Oct 6 11:02:05.223 CDT: %LINK-3-UPDOWN: Interface ATM0/0/0, changed state to up

Oct 6 11:02:06.223 CDT: %LINEPROTO-5-UPDOWN: Line protocol on Interface ATM0/0/

0, changed state to up

Oct 6 11:02:06.351 CDT: %PIM-5-DRCHG: DR change from neighbor to 10.15

.254.2 on interface ATM0/0/0

Oct 6 11:02:07.919 CDT: %PIM-5-NBRCHG: neighbor UP on interface AT


Oct 6 11:03:52.922 CDT: %PIM-5-NBRCHG: neighbor DOWN on interface

ATM0/0/0 non DR


ATM0/0/0 is up, line protocol is up

Hardware is HWIC-DSLSAR (with Alcatel ADSL Module)

Internet address is

MTU 4470 bytes, sub MTU 4470, BW 512 Kbit, DLY 1000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ATM, loopback not set

Encapsulation(s): AAL5 AAL2, PVC mode

23 maximum active VCs, 256 VCs per VP, 1 current VCCs

VC Auto Creation Disabled.

VC idle disconnect time: 300 seconds

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters 6d07h

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: Per VC Queueing

30 second input rate 0 bits/sec, 0 packets/sec

30 second output rate 0 bits/sec, 0 packets/sec

984032 packets input, 500586163 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

838225 packets output, 106313349 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 output buffer failures, 0 output buffers swapped out


There are several hundred routers having the same problem lately which connected different ISP.

I think there are 3 ways to drop default route route

A. My NIC has problem.

B. The DSLAM has problem on

C. IOS has changed about 8 weeks ago. I am using Version 12.4(13r)T

D. I am planning to add a static route with AD = 21, hopefully, the static would connect to ISP, when default is gone.

Anyother suggestion?


Re: BGP default goes disappeared sometime

What you can see is that, during the failure, the has disappeared from the 'sh ip bgp'!! This shouldn't be possible, because you are learning teh default from a eirgp neighbor. The entry in the routing table hasn't been flushed for hours!!