Monday, November 1, 2021

Cisco 9200L's MAC Learning Issues

Hello all,

I was just wondering if I'm the only one that has come across issues with 9200L's learning MAC addresses on legacy devices? Thus far I've found older Star TSP800II printers, older Netgear hubs (I know they shouldn't be on the network, it's not my choice), and some older medical equipment. TAC has been unhelpful. I've demonstrated to them that 3750x's and 2960x's have no issues with these legacy devices. I've been told to to upgrade the software to the latest version that came out a few weeks ago with the only resolved caveat being related to QoS.

In some cases the switches will learn the MAC's correctly but the endpoints are still unable to communicate across the network. Below is my latest encounter with the issue, I have two hosts behind a hub (against my will).

show int (I notice the output drops, has me curious)

GigabitEthernet1/0/7 is up, line protocol is up (connected) Hardware is Gigabit Ethernet, address is 20cf.aed9.7787 (bia 20cf.aed9.7787) MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX input flow-control is on, output flow-control is unsupported ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:01:54, output 00:00:00, output hang never Last clearing of "show interface" counters 2d19h Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 537705 Queueing strategy: Class-based queueing Output queue: 0/40 (size/max) 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 205902 packets input, 14924441 bytes, 0 no buffer Received 205902 broadcasts (4898 multicasts) 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog, 4898 multicast, 0 pause input 0 input packets with dribble condition detected 0 packets output, 0 bytes, 0 underruns Output 0 broadcasts (0 multicasts) 0 output errors, 0 collisions, 3 interface resets 0 unknown protocol drops 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier, 0 pause output 0 output buffer failures, 0 output buffers swapped out 

sh mac address-table int

Vlan Mac Address Type Ports ---- ----------- -------- ----- 64 10e7.c65f.bbc9 DYNAMIC Gi1/0/7 64 a4bb.6dad.1e37 DYNAMIC Gi1/0/7 

Going to my core and checking the ARP table:

Internet 10.1.64.15 56 10e7.c65f.bbc9 ARPA Vlan64 Internet 10.1.64.53 56 a4bb.6dad.1e37 ARPA Vlan64 

Attempting to ping these from the core:

Sending 5, 100-byte ICMP Echos to 10.1.64.15, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) Sending 5, 100-byte ICMP Echos to 10.1.64.53, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) 

Now as soon as these are moved back to the very old 2950 on-site, it works fine. Any thoughts are greatly appreciated.

Edit: Configurations are identical between the two switches.

Thanks!



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