Are discards in MetroCluster IP a problem?
Applies to
- MetroCluster IP
- Discarded packets on:
- MetroCluster IP interfaces (ifstat -a)
- IP switch ports
Answer
- Discards are packets that were dropped by the receiving side, for example a MetroCluster IP port or IP switch ISL
- <0.01% of the total frames being discarded are no reason for concern
- A possible reason is, the node was not able to process the data fast enough and had to free buffer
Example ifstat -a:
-- interface e0a (5 days, 22 hours, 5 minutes, 38 seconds) --
RECEIVE
Total frames: 281m | Frames/second: 550 | Total bytes: 523g
Bytes/second: 1023k | Total errors: 0 | Errors/minute: 0
Total discards: 397 | Discards/minute: 0 | Multi/broadcast: 201k
Non-primary u/c: 0 | CRC errors: 0 | Runt frames: 0
Fragment: 0 | Long frames: 0 | Jabber: 0
Length errors: 0 | No buffer: 0 | Xon: 0
Xoff: 0 | Pause: 0 | Jumbo: 59896k
Noproto: 0 | Error symbol: 0 | Illegal symbol: 0
Bus overruns: 0 | Queue drops: 397 | LRO segments: 153m
LRO bytes: 510g | LRO6 segments: 0 | LRO6 bytes: 0
Bad UDP cksum: 0 | Bad UDP6 cksum: 0 | Bad TCP cksum: 0
Bad TCP6 cksum: 0 | Mcast v6 solicit: 0 | Lagg errors: 0
Lacp errors: 0 | Lacp PDU errors: 0
Example show interface counters:
(IP_Switch_A_1)#show interface counters
Port InOctets InUcastPkts InMcastPkts InBcastPkts InDropPkts Rx Error
--------- ---------------- ---------------- ---------------- ---------------- ---------------- ----------------
...
0/9 549513604412 273572881 22211 16211 6 0
0/10 628951591621 303989361 22205 15478 1 0
...
0/13 189815444917 64098423 326062 0 103883 0
0/14 244671882280 60326655 103750 967 103834 0
0/15 330534040767 126059963 103749 849 104613 0
0/16 284351836716 70305010 103749 0 103793 0
0/55 190457301 40571 547474 48752 5987 0
0/56 256473241 102376 103751 1346 5032 0
If the amount of discards is higher than 0.01%:
Additional Information
- Latency and packet loss limits in the ISLs
- Discarded packets should not be confused with packet loss
- "Packet loss" means the packet never reached the destination interface.
- Discards mean the packet reached the destination and was dropped there