Just looking for some ideas to troubleshoot a Mgt Vlan issue. We have quite a large, flat L2 network running RSTP and have been having issues with the VLAN for some time. Basically its flakey with some switches (and devices behind them) dropping packets and inaccessible on Vl10. In such cases its possible to an extended ping to the device which wakes it up and then apparently populates the ARP cache. Vlan 10 interfaces are also showing ?ignored? errors and, to a lesser extent, ?throttles?.
? Approx 15 x 2950s run at aggregation layer and terminate on a 6506
? No physical errors on the trunk interfaces. No bandwidth saturation issues.
? High number ARP Vs IP packets on the mgt VLAN. Debug ARP showed no problems.
? Large number of throttles in Vlan.
? Large number of broadcasts in Vlan (especially in relation to input traffic).
? Large number of ignored packets in Vlan. Ignored packets are normally symptomatic of buffer/CPU issues which is not the case and Cisco docs don?t offer any further troubleshooting advice.
? ?Storm-control broadcast level x.x? and ?storm-control action trap? have been enabled on the trunk ports along with the ?allowed VLAN? cmd.
? The ARP time out default has also been changed from the default to 5 minutes to no effect (may account for some of the additional ARP traffic).
? There are also some trunks running the ?native vlan 10? cmd which Im not able to remove as it prevents access to the devices behind it. Carrying untagged traffic into Vlan may be an issue but wouldn?t be responsible for ?ignored? packets?
? Mgt VLAN is also using process switching.
Anyone had any similar issue or any ideas re any further troubleshooting? An example output from one of the 2950s below.
*Ignored and b?cast packets*
2950_01#sh int vlan 10
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 87000 bits/sec, 139 packets/sec
5 minute output rate 468000 bits/sec, 62 packets/sec
648641484 packets input, 1576333980 bytes, 0 no buffer
Received 266803178 broadcasts (0 IP multicast)
0 runts, 0 giants, 195206 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 132075465 ignored <<< IGNORED!
378481703 packets output, 1285951018 bytes, 0 underruns
** Physical Trunk**
2950_01#sh controllers ethernet-controller g0/1
473263562 Bytes 2493608151 Bytes
4139804096 Frames 960683870 Frames
63007766 Multicast frames 31 FCS errors
27809995 Broadcast frames 165735724 Multicast frames
0 Pause frames 399656139 Broadcast frames
**ARP Vs IP Packets**
2950_01#sh int vlan 10 accounting
Protocol Pkts In Chars In Pkts Out Chars Out
IP 35962865 22840592 33196205 3594660941
ARP 133006620 3687132588 590645 35438700
***ARP Vs IP Packets**
B2SH_2950_01#sh int vlan 10 switching
Throttle count 195514
Protocol Path Pkts In Chars In Pkts Out Chars Out
IP Process 35978520 30711457 33210601 3602399851
ARP Process 133160464 3696367358 590978 35458680
2950_01#sh run int vl10
ip address x.x.x.x x.x.x.x
no ip route-cache
arp timeout 300
2950_01#sh proc cpu | ex 0.00
CPU utilization for five seconds: 19%/9%; one minute: 15%; five minutes: 15%