cisco router not accessible

[aliver]

Good day!

We had cisco 2621 and sometimes it became not accessible, but anyway we received syslog messages,such as

Apr 25 01:54:52.028 MSD: %RADIUS-4-RADIUS_DEAD: RADIUS server 192.168.12.1:1812,1813 is not responding.

Apr 25 01:54:52.028 MSD: %RADIUS-4-RADIUS_ALIVE: RADIUS server 192.168.12.1:1812,1813 has returned.

Apr 25 01:55:01.852 MSD: %RADIUS-4-RADIUS_DEAD: RADIUS server 192.168.12.1:1812,1813 is not responding.

Apr 25 01:55:01.852 MSD: %RADIUS-4-RADIUS_ALIVE: RADIUS server 192.168.12.1:1812,1813 has returned.

Apr 25 01:55:03.580 MSD: %RADIUS-4-RADIUS_DEAD: RADIUS server 192.168.20.1:1812,1813 is not responding.

Apr 25 01:55:03.580 MSD: %RADIUS-4-RADIUS_ALIVE: RADIUS server 192.168.20.1:1812,1813 has returned.

Apr 25 01:55:09.884 MSD: %RADIUS-4-RADIUS_DEAD: RADIUS server 192.168.12.1:1812,1813 is not responding.

Apr 25 01:55:09.884 MSD: %RADIUS-4-RADIUS_ALIVE: RADIUS server 192.168.12.1:1812,1813 has returned.

Apr 25 01:55:12.860 MSD: %RADIUS-4-RADIUS_DEAD: RADIUS server 192.168.20.1:1812,1813 is not responding.

Apr 25 01:55:12.860 MSD: %RADIUS-4-RADIUS_ALIVE: RADIUS server 192.168.20.1:1812,1813 has returned.

We changed it to cisco 2821, but today night it became not accessible again with the same symptoms and syslog messages.

After rebootting everything were OK in both cases.

What kind of trouble may be in this case?

Thanks!

[atif.awan]

When you say it becomes inaccessible do you mean you cannot telnet to it or does it stop responding to ICMP echoes also? Does the router also stop forwarding traffic?

It seems as your AAA server (Radius) is not responding. Are you using AAA for securing router management? If yes then can you please show us the AAA configuration of the router; usually a fallback mechanism is configured for situations when the primary AAA mechnism does not respond.

[aliver]

inaccessible mean that it stops responding to anything requests (telnet,icmp,snmp). But during same time syslog messages from it continued recieved. But syslog is one-way protocol and doesn't need answer. So is it perhaps a traffic recieve trouble of cisco router?

I don't know does the router also stop forwarding traffic or not,because we did'n check it yet because of importance of router and we reset the power immediately.

AAA server is used for securing router management only. Config is simple:

aaa authentication username-prompt "login: "

aaa authentication login default local group radius enable

aaa authorization exec default local group radius

!

And as i think radius syslog messages are originate from router inaccessibility because there are not any messages when it works in normal state. I've shown theirs in hope something strange you see in them that helps find a problem. The question is not in radius! Question - what are there possible causes of inaccessibility? error in ethernet controller or something else?