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Etherchannel on 3640 etherswitch module

I have a customer whose lan interface (100mb) gets overrun by data at various times of the day. Wondering if I can use a etherswitch module with etherchannel set up to a 6509 switch also with etherchannel and increase the net bandwidth. The new etherchannel interface would need to support routing and hsrp. Also, would I take a major processor/memory hit for this?

9 REPLIES

Re: Etherchannel on 3640 etherswitch module

Hello,

I do not know enough of the traffic pattern to suggest whether an etherchannel would resolve your customer's b/w problem but I can tell you that an etherswitch module does support channeling. On certain IOS the etherswitch module ports can also be configured for Layer 3 interfaces and with that the channel can be a layer 3 channel interface. But It is better to make it a Layer 2 channel, it is a switch after all, and you can make it trunk or an access channel (belonging to single vlan) then you can create an interface vlan on the 3640 which would be your layer 3 for a routed interface and for HSRP.

Here is an etherswitch module configuration guide to help you start:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t11/ft1636nm.htm#wp1434673

Please rate helpful posts.

Purple

Re: Etherchannel on 3640 etherswitch module

Should work for what you want it to do . Etherchanneling puts very little overhead on the cpu.

New Member

Re: Etherchannel on 3640 etherswitch module

I am afraid I am going to have to disagree with Glen on this one. Although I have no reason to doubt his claim that Etherchannel puts little overhead on the CPU a major issue you are faced with is the fact that Etherchannel does not actually load balance on a per bit basis. Rather Etherchannel simply splits traffic (by default) by using source and destination MAC addresses. Depending on the nature of your traffic it is entirely possible that all the traffic will crowd onto one wire and leave the other wire unused.

Another concern, if you are over utilizing the LAN side of a router what kind of outbound queues are you looking at on the WAN interfaces? (I assume the router is only connected to one LAN and multiple WAN links.)

Purple

Re: Etherchannel on 3640 etherswitch module

Well he doesn't even mention anything about wan links . Unless he has traffic that is like 2 hosts that runn the same traffic it is going to get distributed fairly evenly across that channel . Is it going to be exactly even distribution , probably not . He can change the etherchannel so that it looks at both the source and destination ip addresses and it will balance it on those . It will get fairly evenly distributed across those links if you have a variety of different users coming across that link , its exactly what etherchannel is for .

New Member

Re: Etherchannel on 3640 etherswitch module

Well yes, in theory. But in my experience what works wonders in theory often times needs to go back to the lab in practice. Glen, have you ever applied MRTG (or any other traffic grapher) to an etherchannel deployment? We use it between our 3750s and the core 6509s and the results have been less than satisfactory.

In any case my major concern: consider, you have a router connected to a LAN, the connection is now, (we'll assume a well balanced working Etherchannel) 200Mbps. What sort of outbound links are there? As I recall the original message implied that there was one full blast 100Mbps link and a bunch of WAN links, unless those WAN links are all FDDI, or T3 or something big like that (OC-3, whatever) the big concern here won't be the speed you are picking up bits off the LAN side, rather the issue is the speed you are dumping bits onto the WAN side.

I'd like to get more information before making a definite Etherchannel will/not work here, call. I would say deploy MRTG first, then see what you really need to improve. My money is on a slow WAN link, but that's just my $0.02.

Michael

Purple

Re: Etherchannel on 3640 etherswitch module

Yes you are correct I guess I didn't catch that he was going to a router and he wanted to etherchannel to that and then over a wan link , that would then be a major choke point and he would be better off getting a bigger wan pipe before or conjunction with using etherchannel . If he is saying that the 100 meg connecting link is full then the wan links would have to be really saturated.

New Member

Re: Etherchannel on 3640 etherswitch module

No,I'm not going the the WAN it would be outbound to another LAN interface that I would like to etherchannel as well. The WAN side of things isn't really an issue. What's causing my concern is that at peak times during the day I have traffic that is moving from one LAN to another and the traffic will go through the roof and cause the CPU to max out.

Purple

Re: Etherchannel on 3640 etherswitch module

If you are going lan to lan then yes etherchannel should help . It should have little effect on the cpu everything is fast switched using cef which should have very little impact on the cpu itself , I would check to see if CEF is enabled...

New Member

Re: Etherchannel on 3640 etherswitch module

If you are going LAN to LAN and I assume you are passing through a router because they are different subnets, why not use the routing features on the 6509 and route at potentially 720 Gbps instead of a measly 200 Mbps? FYI, Cisco is end of lifing the 3640 this November.

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