[e-nsp] x650 and MAC addresses missing in FDB ????

[Marcin Kuczera]

Erik Bais wrote:
> Hi Marcin,
> 
> Have you checked what kind of traffic it might be ?
> Did you enable IGMP snoop and MLD snoop

Both enabled

> Is the traffic limited to 1 single vlan or is it a specific vlan / type traffic that causes this ? Microsoft NLB comes to mind ...

It is not specific vlan, it is random behaviour.

traffic is regular IPv4:
21:09:25.276836 00:30:88:19:32:a5 > 98:fc:11:cb:7b:ce, ethertype 802.1Q 
(0x8100), length 1518: vlan 3408, p 0, ethertype IPv4, (tos 0x20, ttl 
53, id 49068, offset 0, flags [DF], proto TCP (6), length 1500)
     216.155.151.93.80 > 188.137.52.217.49460: Flags [.], seq 
322060:323520, ack 1, win 29, length 1460
21:09:25.276839 00:30:88:19:32:a5 > 98:fc:11:cb:7b:ce, ethertype 802.1Q 
(0x8100), length 1518: vlan 3408, p 0, ethertype IPv4, (tos 0x20, ttl 
53, id 49069, offset 0, flags [DF], proto TCP (6), length 1500)
     216.155.151.93.80 > 188.137.52.217.49460: Flags [.], seq 
323520:324980, ack 1, win 29, length 1460
21:09:25.276841 00:30:88:19:32:a5 > 98:fc:11:cb:7b:ce, ethertype 802.1Q 
(0x8100), length 1518: vlan 3408, p 0, ethertype IPv4, (tos 0x20, ttl 
53, id 49070, offset 0, flags [DF], proto TCP (6), length 1500)
     216.155.151.93.80 > 188.137.52.217.49460: Flags [.], seq 
324980:326440, ack 1, win 29, length 1460

i.e. 98:fc:11:cb:7b:ce is not in FDB and after several seconds it 
appears, u-unicast traffic is gone for that host, but then I have 
another hosts with such traffic with no entry in FDB.
Ok, in many cases it would be correct but not in ours..

When particular DST MAC is broadcasted (unknown-unicast) it apears in 
FDB of next switch in chain towards DST (x450), then also I could see 
that age timer refreshes ! and - this MAC is still not in FDB of x650.


On x650 I have almost 500 VLANs, 13k MAC addresses in FDB.

I don't see this behaviour on x450 switches...

Regards,
Marcin







> Regards,
> Erik
> 
> 
> -----Original Message-----
> From: extreme-nsp-bounces at puck.nether.net [mailto:extreme-nsp-bounces at puck.nether.net] On Behalf Of Marcin Kuczera
> Sent: woensdag 28 december 2011 20:39
> To: extreme-nsp at puck.nether.net
> Subject: Re: [e-nsp] x650 and MAC addresses missing in FDB ????
> 
> Well,
> I'am recalling my issue, maybe someone has a proper contact to someone from Extreme R&D.
> 
> at the moment we have about 13k in FDB, and up to 25Mbit/s of unknown-unicasts traffic...
> This is getting nasty...
> 
> I need to know if x650 has a probablity that not all MAC may be represented in FDB (still below 32k limit).
> 
> Regards,
> Marcin
> 
> 
> 
> 
> Marcin Kuczera wrote:
>> Marcin Kuczera wrote:
>>> hello,
>>>
>>> I have noticed an issue, that sometimes some mac addresses are not
>>> visible in FDB on x650 stack.
>>>
>>> I have several x450 in chain-patch from customer and then x650 where
>>> router is connected to.
>>>
>>> I could see MAC addresses for particular hosts in all x450 chain, but
>>> it was missing in x650 for most of the time. Then sometimes it appeard.
>>>
>>> How do I catch them ? I'am monitoring unicast flooding on all vlans
>>> and I have a lot of such cases...
>>>
>>>
>>> EXOS release is 12.5.4.5 v1254b5-patch1-4 numer of MAC addresses in
>>> FDB osscilates around 14k max, but this is not a problem because fdb
>>> capacity in x650 is 32k.
>>>
>>> Nothing in logs..
>>>
>>> It is not tooo nasty, but I'am wondering if it is not some bug that
>>> may affect some other services, i.e. multicasts.
>> well, I spoke to an extreme engineer and he mentioned, that this might
>> be some issue related to fdb hashing mechanism..
>>
>> It is supposed to be multi-level hashing, however it might be, that
>> the lowest level "container" capacity, that contains whole MAC address
>> - is limited.
>> So, if there are some MAC addresses that will match this lowest level
>> "container", and let's say - the limit per "container" is 16, and we
>> have 17th MAC matching - it will not be placed there due to no space,
>> and the traffic will be flooded...
>>
>>
>> Is there anyone here that could verify this thesis ?
>> How do I debug it ?
>>
>>
>> Regards,
>> Marcin
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