Nortel 8600 indiscards

[leedsit]

Hi,

We have 6 8600`s all SMLT Trunked togethor with 2 at the core running an IST between them and then connecting to the other switches at L2 with Multiple vlan Split multi link trunks.

On the 4 Nortel 8600 switches on the fibre ports that have the SMLT, there a thousands of Indiscard packets ( counters say so ). has anyone come across these before, the Nortel web site has nothing ( spend hours trawling though it ).

Any help would be appreciated to determin if this is normal ( I.E non loop mechnasim of the MLT ) or something a little more sinister.


LEEroy
MCNE6,CCNP,CWNA,CCSA,Project+

 

[anthonyanderberg]

Traditionally inDiscard packets are different than inError packets in that inDiscards are packets that don't have anything wrong with them. The inError packet counter is the sum of all of the packets that were found to be corrupt in some way (bad CRC, FCS, alignment, ect.)

It’s possible the reason for discarding such packets could be to free up buffer space because of some kind of internal bottleneck. I wonder if the 8600 would increment this counter when a packet arrived tagged for a VLAN that didn't exist in that particular box? Is the counter constantly incrementing, does it come in bursts?

On a personal note, I'm considering migrating from a layer-3 (OSPF) backbone to an SMLT-based layer-2 backbone so I can support VLAN tags. I'd be interested in anything you'd have to say about the SMLT/L2 in terms of reliability and ease of troubleshooting. - Thanks.

 

[leedsit]

Hi,

Thanks for the reply, I have just checked and the Core 8600`s do trunk extra vlans to the edge 8600`s... Good spot... Ill see if I can get this removed(not sure why its been done but I was not my install )... and recheck... and there`s me checing out QOS and rate limit settings....

With regards to the Layer 2 SMLT... I was a cisco guy ( and still am to an extent )... but I love these 8600`s... The site that has the 6x8600`s in a SMLT configuration has been running non stop for 3 years. We have lost some fibre ports, even a card, but because we spread the fibres across multiple cards etc, we have yet to experience loss of service to the users ( 100 Uptime over 3 years is not bad! ).... So I would totally recommend this configuration.
Reliability, obviously give 100%... Trouble shooting... Ive not really had to, they look after themselfs ( apart from this issue of course ).

HTH, Lee.

LEEroy
MCNE6,CCNP,CWNA,CCSA,Project+

 

[Jynxx]

InErrors are the total amount of packets that "had errors" that prevented them from being delivered, such as if you have a speed/duplex mismatch and get alignment errors, FCS, frame too shorts, etc (as mentioned).

If you literally add them up, they will be identical to the InErrors field. If InErrors increment, I would look at speed/duplex settings.

However if your InDiscards are incrementing regularly and your InErrors are not, it is likely a buffer issue that results in the drop, and as anthony mentioned, can be caused from inproperly configured VLANs, where there is a VLAN on one side of the link and not on the other. Generally the side that you are taking the InDiscards on is the side without the VLAN.

 

[neilchapman]

Anthony Anderberg mentioned that he wanted to get rid of OSPF to make use of SMLT's in his 8600's. You don't have to.

There is an option in the 8600's called RSMLT's

Routed Switched Multi-Linked Trunks

If you thought SMLT's were cool, RMSLT's will make you giggly.

RSMLT's work like this...

Two 8600's are connected w/IST's
Distribution or Access switches have VLANs with their gateway IP on the core switches
The VLAN(s) have their gateway IP shared between the 8600's WITHOUT any VRRP or other tools L3 tools required.
If one core goes down, the gateway continues to respond on the redundant switch.

How cool is that! The switch is so fast that you wont lose a VoIP call.

This is a one click configuration.

FYI - even the the 5500's w/V5 code can do IST's the RSMLT feature is reserved for the 8600 family.

Don't give up your OSPF core!

Good Luck