Intermittent Telnet to 2950

pankajs · ‎09-16-2009

I have a 2950 switch which is behind a Cisco PIX (7.0).

While trying to telnet to 2950 the connection is intermittent. Sometimes telnet works and sometimes not(no login prompt). Below is the capture on PIX.

1: 04:42:16.747626 10.194.1.106.47552 > 10.194.3.30.23: S 196858349:196858349(0) win 49640 <mss 1380,nop,nop,sackOK>

2: 04:42:16.750724 10.194.3.30.23 > 10.194.1.106.47552: S 2189688705:2189688705(0) ack 196858350 win 4128 <mss 536,[bad opt]>

3: 04:42:18.750800 10.194.3.30.23 > 10.194.1.106.47552: S 2189688705:2189688705(0) ack 196858350 win 4128 <mss 536,[bad opt]>

4: 04:42:20.109872 10.194.1.106.47552 > 10.194.3.30.23: S 196858349:196858349(0) win 49640 <mss 1380,nop,nop,sackOK>

5: 04:42:20.111505 10.194.3.30.23 > 10.194.1.106.47552: . ack 196858350 win 4128

6: 04:42:22.750800 10.194.3.30.23 > 10.194.1.106.47552: S 2189688705:2189688705(0) ack 196858350 win 4128 <mss 536,[bad opt]>

7: 04:42:26.859910 10.194.1.106.47552 > 10.194.3.30.23: S 196858349:196858349(0) win 49640 <mss 1380,nop,nop,sackOK>

8: 04:42:26.861558 10.194.3.30.23 > 10.194.1.106.47552: . ack 196858350 win 4128

9: 04:42:30.750800 10.194.3.30.23 > 10.194.1.106.47552: S 2189688705:2189688705(0) ack 196858350 win 4128 <mss 536,[bad opt]>

10: 04:42:40.360165 10.194.1.106.47552 > 10.194.3.30.23: S 196858349:196858349(0) win 49640 <mss 1380,nop,nop,sackOK>

11: 04:42:40.361812 10.194.3.30.23 > 10.194.1.106.47552: . ack 196858350 win 4128

12: 04:42:46.750052 10.194.3.30.23 > 10.194.1.106.47552: S 2189688705:2189688705(0) ack 196858350 win 4128 <mss 536,[bad opt]>

13: 04:42:49.674601 10.194.3.30.123 > 10.194.255.1.123: udp 48

14: 04:42:49.674952 10.194.255.1.123 > 10.194.3.30.123: udp 48

15: 04:43:07.360577 10.194.1.106.47552 > 10.194.3.30.23: S 1544225147:1544225147(0) win 49640 <mss 1380,nop,nop,sackOK>

16: 04:43:07.362194 10.194.3.30.23 > 10.194.1.106.47552: . ack 196858350 win 4128

17: 04:43:07.362499 10.194.1.106.47552 > 10.194.3.30.23: R 196858350:196858350(0) win 49640

10.194.1.106 is management station and 2950 mgmt. interface is 10.194.3.30. Pix outside interface and switch mgmt. are in same subnet.

Thank you.

rducombl · ‎09-17-2009

HI,

Can you get sh interface vlan xxx for your management interface.

look in it if there are throttles. 2950 do not have very powerfull cpu and can be exposed to low telent connectivity is the cpu is busy processing other packet.

this is often the case with multicast, if you do not need/run multicast you can try disable ip igmp snooping on 2950 and see if it helps.

Cheers,

Roland