gigabit ethernet interfaces on 3845 and keepalives

Answered Question
Apr 23rd, 2007

Hi, I have a 3845 with IOS 12.4(11)T1 (needs this IOS for CME).

I am attempting to do simple redundancy on the gigabit ethernet by setting G0/1 as a backup interface to G0/0 using "backup interface G0/1" on G0/0.

All is working fine apart from one problem. Everytime I reboot the router, both internal gigabit ethernet interfaces have the "no keepalives" command assigned to them.

This command is not in the startup config and is also not the default. This occurs whether the ethernet ports are connected to a switch or not.

This stops the redudancy working as the router does not detect the gigabit ethernet interface going down.

Any ideas?

Thanks

David

I have this problem too.
0 votes
Correct Answer by sundar.palaniappan about 9 years 9 months ago

David,

I am afraid you are hitting this IOS bug.

CSCsg68683 Bug Details

Headline c3800: GigabitEthernet interface keepalive settings change at boot-time

Product IOS

Feature 3800 Component Components Duplicate of

Severity 3 Severity help Status Resolved Status help

First Found-in Version 12.4(10.5), 12.4(10.5)T, 12.4(08b), 12.4(10a), 12.4(12.2)T, 12.4(11.06b) All affected versions First Fixed-in Version 12.4(9)T03, 12.4(12a), 12.4(12.15), 12.4(12.15)T, 12.4(07e) Version help

Release Notes

Symptoms:

=========

The keepalive N command under a GigabitEthernet port changes its setting at

router boot-time. For the following startup-config:

!

interface GigabitEthernet0/0

ip address dhcp

duplex auto

speed auto

media-type rj45

keepalive 15

!

interface GigabitEthernet0/1

no ip address

duplex auto

speed auto

media-type rj45

!

we see the following happen at boot-time:

(1) GigE0/0 with keepalive 15 NVGENs to not having the command show at all --

it thinks the keepalive has been set to defaults.

(2) GigE0/1 with no explicit keepalive N command NVGENs no keepalive.

After boot-time it is found that the following happens:

(3) If I assert keepalive N on either interface then the desired command does

NVGEN, but will be affected by (1) at the next reboot if the current config

is saved to NVRAM.

(4) If I set default keepalive, then there is no keepalive N command NVGENed

-- it thinks the keepalive has been set to defaults. It is affected by (2)

at the next reboot if the current config is saved to NVRAM.

Conditions:

===========

This behaviour WILL BE observed on Cisco 3825 and 3845 routers which are

installed with an IOS specified by or implied by the "First Fixed-in" field of

bug ID CSCek46943 "700-800 msec ping delay occurs for Gig-eth int of c3800".

This is a sufficient condition for the problem symptom to occur; no special

configuration is necessary. This problem is not observed on a Cisco 2821 or

2851 installed with the same version of IOS.

Workaround:

===========

There is no known workaround other than to use an unaffected IOS release.

HTH

Sundar

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Correct Answer
sundar.palaniappan Mon, 04/23/2007 - 14:12

David,

I am afraid you are hitting this IOS bug.

CSCsg68683 Bug Details

Headline c3800: GigabitEthernet interface keepalive settings change at boot-time

Product IOS

Feature 3800 Component Components Duplicate of

Severity 3 Severity help Status Resolved Status help

First Found-in Version 12.4(10.5), 12.4(10.5)T, 12.4(08b), 12.4(10a), 12.4(12.2)T, 12.4(11.06b) All affected versions First Fixed-in Version 12.4(9)T03, 12.4(12a), 12.4(12.15), 12.4(12.15)T, 12.4(07e) Version help

Release Notes

Symptoms:

=========

The keepalive N command under a GigabitEthernet port changes its setting at

router boot-time. For the following startup-config:

!

interface GigabitEthernet0/0

ip address dhcp

duplex auto

speed auto

media-type rj45

keepalive 15

!

interface GigabitEthernet0/1

no ip address

duplex auto

speed auto

media-type rj45

!

we see the following happen at boot-time:

(1) GigE0/0 with keepalive 15 NVGENs to not having the command show at all --

it thinks the keepalive has been set to defaults.

(2) GigE0/1 with no explicit keepalive N command NVGENs no keepalive.

After boot-time it is found that the following happens:

(3) If I assert keepalive N on either interface then the desired command does

NVGEN, but will be affected by (1) at the next reboot if the current config

is saved to NVRAM.

(4) If I set default keepalive, then there is no keepalive N command NVGENed

-- it thinks the keepalive has been set to defaults. It is affected by (2)

at the next reboot if the current config is saved to NVRAM.

Conditions:

===========

This behaviour WILL BE observed on Cisco 3825 and 3845 routers which are

installed with an IOS specified by or implied by the "First Fixed-in" field of

bug ID CSCek46943 "700-800 msec ping delay occurs for Gig-eth int of c3800".

This is a sufficient condition for the problem symptom to occur; no special

configuration is necessary. This problem is not observed on a Cisco 2821 or

2851 installed with the same version of IOS.

Workaround:

===========

There is no known workaround other than to use an unaffected IOS release.

HTH

Sundar

davidstevenscisco Mon, 04/23/2007 - 23:15

Hi Sundar,

Many thanks for this. I looked in the bug toolkit myself but did not find it. This really helps me realise I am not going crazy!

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