[c-nsp] FW: Overruns

Emanuel Popa emanuel.popa at gmail.com
Thu May 6 05:43:14 EDT 2010


One more thing that comes to mind: load-balancing algorithm for
ether-channels with 5 links on Cisco 7600 is pretty tricky:
http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a0080094714.shtml

This means that on an ether-channel with 5 GE links, considering the
hashing algorithm documented by Cisco and good entropy, you will have:
- max. 1000Mbps on link #1
- max. 1000Mbps on link #2
- max. 1000Mbps on link #3
- max. 500Mbps on link #4
- max. 500Mbps on link #5
- max. 4000Mbps (4Gbps) on the ether-channel

So why not using only 4 links in the ether-channel instead of 5?

Regards,
Manu


2010/5/5 Mohammad Khalil <eng_mssk at hotmail.com>:
> no , there is no congestion at all either in ingress or egress direction
> and the overruns vary from one individual physical link to another
>
>> Date: Wed, 5 May 2010 13:05:42 +0300
>> Subject: Re: [c-nsp] FW: Overruns
>> From: emanuel.popa at gmail.com
>> To: eng_mssk at hotmail.com
>> CC: cisco-nsp at puck.nether.net
>>
>> Sorry. I'm not very familiar with that kind of linecards. Only using
>> LAN cards 67xx with DFC modules.
>>
>> However, when we encountered overruns we had 2 options:
>>
>> 1. easy one: enable "fabric clear-block"; this will get rid of
>> overruns but will drop packets in fabric which is gonna be harder to
>> detect; the fabric is only going to internally prioritize CoS 5 with
>> older IOS versions; with newer versions might be another story; never
>> tested though
>>
>> 2. more difficult: "ingress queuing" is necessary to overrun only
>> packets you afford to drop, but can be done only with CoS and 802.1q
>> configured on your ether-channels
>>
>> Anyways, is there any congestion at the egress in your router that is
>> causing the overruns in the first place? Or is this a different
>> problem than what we experienced?
>>
>> Regards,
>> Manu
>>
>>
>> 2010/5/5 Mohammad Khalil <eng_mssk at hotmail.com>:
>> > The cards are SFM-capable 48 port 10/100/1000mb
>> > we connect 10 connections from each router to the ASN , each 5 are
>> > grouped
>> > together , 5 for VLAN that handle RAS to ASN communication and the other
>> > 5
>> > to handle ASN to Core communication
>> >
>> >> Date: Tue, 4 May 2010 23:50:31 +0300
>> >> Subject: Re: [c-nsp] FW: Overruns
>> >> From: emanuel.popa at gmail.com
>> >> To: eng_mssk at hotmail.com
>> >> CC: cisco-nsp at puck.nether.net
>> >>
>> >> hi mohammad,
>> >>
>> >> what kind of linecards are you using? what capacity? how many links
>> >> per ether-channel?
>> >>
>> >> we had similar problems with overruns at ingress because of egress
>> >> congestion. there are different workarounds for each setup. all
>> >> problems are related to buffers and fabric connections though.
>> >>
>> >> regards,
>> >> manu
>> >>
>> >>
>> >> 2010/5/4 Mohammad Khalil <eng_mssk at hotmail.com>:
>> >> >
>> >> > hi all
>> >> >
>> >> > i posted this issue earlier but didnt get a solution
>> >> > anyway the MTU settings from both side are the same 1500 bytes
>> >> > i dont think that the MTU modification from Cisco side as its related
>> >> > to
>> >> > the number of packets sent from the ASN side and received by the
>> >> > Cisco side
>> >> > i was viewing the buffers on the Cisco side and found below
>> >> > Public buffer pools:
>> >> >
>> >> > Huge buffers, 18024 bytes (total 2, permanent 2, peak 11 @ 5w5d):
>> >> >     2 in free list (0 min, 4 max allowed)
>> >> >     10062 hits, 182 misses, 364 trims, 364 created
>> >> >     0 failures (0 no memory)
>> >> >
>> >> > do the misses number indicate anything ??
>> >> > does the buffer tuning will solve the issue ?
>> >> > even the IOS upgrade didn't solve the issue
>> >> >
>> >> > Thanks
>> >> >
>> >> > From: eng_mssk at hotmail.com
>> >> > To: cisco-nsp at puck.nether.net
>> >> > Subject: Overruns
>> >> > Date: Tue, 6 Apr 2010 11:44:46 +0300
>> >> >
>> >> >
>> >> >
>> >> >
>> >> >
>> >> >
>> >> >
>> >> >
>> >> > hi all
>> >> >
>> >> > i have 2 cisco 7606 routers connected to ASN GW for wimax traffic
>> >> > we had a problem with overruns on the port channels
>> >> > we connected 5 cables from the ASN to both routers and configured
>> >> > port
>> >> > channels for VLAN and the same setup for another vlan
>> >> > one vlan is for communcations with RASs and one to transport the
>> >> > traffic
>> >> > for into the core cloud
>> >> > anyway we upgraded the IOS version on the routers thinking thats
>> >> > might
>> >> > solve the issue but still
>> >> > please find below
>> >> >
>> >> > CR1.KJ-Building#sh int po10 | inc over
>> >> >     1 input errors, 1 CRC, 0 frame, 72395 overrun, 0 ignored
>> >> > CR1.KJ-Building#sh int po20 | inc over
>> >> >     6 input errors, 2 CRC, 0 frame, 734930 overrun, 0 ignored
>> >> >
>> >> > CR1.KJ-Building#sh run int po10
>> >> > Building configuration...
>> >> >
>> >> > Current configuration : 259 bytes
>> >> > !
>> >> > interface Port-channel10
>> >> >  description CORE_VLAN to ASN Gateway
>> >> >  switchport
>> >> >  switchport access vlan 10
>> >> >  switchport trunk encapsulation dot1q
>> >> >  switchport mode access
>> >> >  load-interval 30
>> >> >  speed 1000
>> >> >  duplex full
>> >> >  flowcontrol receive on
>> >> >  flowcontrol send on
>> >> > end
>> >> >
>> >> > CR1.KJ-Building#sh run int po20
>> >> > Building configuration...
>> >> >
>> >> > Current configuration : 258 bytes
>> >> > !
>> >> > interface Port-channel20
>> >> >  description RAS-VLAN to ASN Gateway
>> >> >  switchport
>> >> >  switchport access vlan 20
>> >> >  switchport trunk encapsulation dot1q
>> >> >  switchport mode access
>> >> >  load-interval 30
>> >> >  speed 1000
>> >> >  duplex full
>> >> >  flowcontrol receive on
>> >> >  flowcontrol send on
>> >> > end
>> >> >
>> >> > CR2.KJ-Building#sh int po10 | inc over
>> >> >     0 input errors, 0 CRC, 0 frame, 17889 overrun, 0 ignored
>> >> > CR2.KJ-Building#sh int po20 | inc over
>> >> >     0 input errors, 0 CRC, 0 frame, 826604 overrun, 0 ignored
>> >> >
>> >> > CR2.KJ-Building#sh run int po10
>> >> > Building configuration...
>> >> >
>> >> > Current configuration : 259 bytes
>> >> > !
>> >> > interface Port-channel10
>> >> >  description CORE_VLAN to ASN Gateway
>> >> >  switchport
>> >> >  switchport access vlan 10
>> >> >  switchport trunk encapsulation dot1q
>> >> >  switchport mode access
>> >> >  load-interval 30
>> >> >  speed 1000
>> >> >  duplex full
>> >> >  flowcontrol receive on
>> >> >  flowcontrol send on
>> >> > end
>> >> >
>> >> > CR2.KJ-Building#sh run int po20
>> >> > Building configuration...
>> >> >
>> >> > Current configuration : 258 bytes
>> >> > !
>> >> > interface Port-channel20
>> >> >  description RAS-VLAN to ASN Gateway
>> >> >  switchport
>> >> >  switchport access vlan 20
>> >> >  switchport trunk encapsulation dot1q
>> >> >  switchport mode access
>> >> >  load-interval 30
>> >> >  speed 1000
>> >> >  duplex full
>> >> >  flowcontrol receive on
>> >> >  flowcontrol send on
>> >> > end
>> >> >
>> >> > any advice in regards
>> >> > thanks
>> >> >
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