Switch to Router Port Channel

[gcarson73]

I have one Cisco 2951 router and a Cisco 3750 switch.  

The router has 3 GB interfaces, 1 interface to the ISP and 2 that I can use for a port-channel to the switch.  I cannot do any testing, since these are used in my "production" environment.  Any advice or input is appreciated.  See my proposed config for each device below.

*Config on Router

en
config t

interface port-channel 1
ip address 10.3.81.1 255.255.255.0
no shut

int g0/1
no ip address
channel-group 1
no shut

int g0/2
no ip address
channel-group 1
no shut

*Config on Switch

en
config t
interface port-channel 1
no switchport
ip address 10.3.81.34 255.255.255.0

int range g1/0/23-24
no switchport
no ip address
channel-group 1 mode on
no shut

[Mark Malone]

Hi

are you sure those routers interfaces are capable of bundling? have logged in and checked is that command available under both ints you want bundle , i didnt think it was supported on 2951

[gcarson73]

I just used the following config on the router.  All looks good, on INT G0/2, I  used a different IP and did not apply to INT G0/1, since that is currently being used.  So that is a good sign this should work.

interface port-channel 1
ip address 192.3.81.1 255.255.255.0
no shut
exit

int g0/2
no ip address
channel-group 1
no shut
exit

[Mark Malone]

yes i had a look at one of our 2951s they have channel-group too just not protocol aware but no real need to be will still work fine, thought you may have needed a hwic but looks good , default route on the switch you should be all set

[gcarson73]

Thank you for checking.  The default route I have (for switch) is

ip route 0.0.0.0 0.0.0.0 10.3.81.1

[Mark Malone]

Yes far side of the portchannel should be good , just make sure you can break out past that interface once applied from the locally connected devices in the switch , once your are your good and if not see where the trace stops that's most likely where the issue is occurring

[paul driver]

Hello

Your L3 link aggregation config looks okay unless what Marks states is applicable and the router IOS doesn't support it?

Note: If it does support it , You may not be able to see any summary information using

sh etherchannel port-channel
                Channel-group listing:
                -----------------------

but wth this:

sh interfaces port-channel 1 | in Des
  Description: TEST LAG





res

Paul

[devils_advocate]

Are you having an issue or just asking if the config looks ok?

I have done a L3 port channel on a 2921 before so I can only assume its supported on the 2951.

The config looks fine to me, the Router cannot do Etherchannel negotiation, hence why the switch side has to be 'on'.

I would schedule a maintenance window though as its likely to blip any production traffic whilst the bundling takes place. 

[gcarson73]

I am not having issues, I am just a 1 man IT person with a small company.  My background is VMware/servers.  We moved from a 2851 to a 2951 router and have the extra GB interface on the router.  I thought I might as well use it.

I applied the config to the switch, but the 2 ports are not connected to the router.  I will schedule some down time.  Will the bundling take a few  minutes?

Do I need any route statement on the switch?

[devils_advocate]

Ahhh I see.

Configuring a Layer 3 port channel is like a point to point link between the Router and the Switch. The switch will need a default route towards the router and the router will need some static (or dynamic) routes for any subnets which exist on the switch.

Thanks

[gcarson73]

In my router I have the route

ip route 0.0.0.0 0.0.0.0 99.3.81.1

so I should add (In my switch)

ip route 0.0.0.0 0.0.0.0 10.3.81.1

10.3.81.1 is interface IP (Channel-group on router), and other interface on router is 99.3.81.66, with the 99.3.81.1 being gateway for my ISP.

[devils_advocate]

Yes that is correct.