Re: Layer 3 Etherchannel Issue

Ross wrote:
On Sep 16, 3:50 pm, fugettaboutit <n...@xxxxxxx> wrote:
Ross wrote:
Dear Group,
I have bought a pair of Catalyst 3750G switches with the advanced IP
services image installed. I am trying to achieve Etherchannel load
balancing using Layer 3 by assigning the port channel an IP address.
---> Keep in mind that an Etherchannel is a L2 entity. However, IOS can
inspect the L3 information of a presented packet, and you can load-share
based on that information. By default, IOS utilizes a MAC hashing/XOR
operation to decide which link to send traffic. As you're probably
already aware, this can be an issue if handing off to a router since the
router could present only one MAC. :-) Utilize the "test etherchannel"
command to verify load-balancing criteria on your Cats.

I

want to be able to send traffic to the IP address assigned to the port
channel and it load balance using src-dst-ip to three backend servers
running a server application which accepts connections on TCP port
1023. All of these servers have Intel ProSet adapters configured for
LACP teaming.
---> In general, force channeling of the Cat interfaces (sounds like
this is already working).



If I assign the port channel an IP address of 192.168.29.254 and each
of the servers teamed NICS a 192.168.29.X address I cannot get any
traffic to the server hosts sending data to the 192.168.29.254 of the
port-channel address. However if i send traffic to TCP port 1023 to
one of the servers teamed NIC 192.168.29.X addresses traffic gets
through.
---> Dump the L3 port-channel interface configuration. Configure the
channel to form as a L2 entity only.



Each of the servers ports on the switch are assigned into the correct
channel port group.
I guess my first question is if what I am trying to acheive possible
using an L3 Etherchannel. And if so what I am doing wrong.
---> I's suggest you configure GLBP on both 3750s. Run each teamed NIC
to a seperate switch. Don't configure L3 teaming on the server; utilize
L2 only. You'll see lots of Intel keepalive traffic over the channel, so
don't panic. Configure the IP stack per normal on the server and assign
it to the L2 NIC team.



I will post a copy of relevant config sections shortly. The two
catalyst switches are in a stack. Each servers dual NIC has a port
assigned on each member of the stack to create the Etherchannel.
IE GigabitEthernet1/0/1 , GigabitEthernet2/0/1 - 1st server
GigabitEthernet1/0/2, GigabitEthernet2/0/2 - 2nd server and so on
Kind Regards
This basic approach should allow you to achieve what you're after:
selection of a channel member link based on L3 packet info, and,
fault-tolerance at L2 (NIC teaming and Etherchannel) and L3 (GLBP). If
anyone else has any thoughts, chime in, but my server team has had
seemingly decent results with this approach.

Will give it a try. I saw the "glbp" command subset on the port-
channel interface but when i tried to assign an IP address it said
command set not supported by switch stack. Do 3750 "G" switches
support it? Or is it just "E" series. Or maybe this is because the
interface is in L3 mode and not L2

Regards

Uggh...sorry about this, but it appears that the 3750 platform *isn't* supported for GLBP, at least according to the CCO Feature Navigator. A quick search on CCO leads to some confusion since GLBP is mentioned in some of the Cat IOS image documentation. So, no, it appears GLBP is a non-starter, however, HSRP looks like it might be an option. You should be able to accomplish same result with HSRP in place of GLBP, but, I think HSRP is a little more arcane to deal with (not a fan of the HSRP group thing...hehe).

Good luck!
.

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