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Network Design - L3 Port-channels

Customer has 3 sites and wish to have a 2 GB circuit to the Metro ring at each site,

The plan is to run EIGRP routing between all three sites.

Not sure if the L3 port-channel will work. Can somebody please advise on this design?

### Metro Ring ###

VLAN 172 is configured on all switches around the Metro ring.

VLAN 172 SVI (172.16.1.1/29) is configued on 7600 switch on the Metro ring.

Customer core switches connect to the Metro switches on VLAN 172 (ports G0/1-2)

3 REPLIES
Hall of Fame Super Blue

Re: Network Design - L3 Port-channels

colmgrier wrote:

Customer has 3 sites and wish to have a 2 GB circuit to the Metro ring at each site,

The plan is to run EIGRP routing between all three sites.

Not sure if the L3 port-channel will work. Can somebody please advise on this design?

### Metro Ring ###

VLAN 172 is configured on all switches around the Metro ring.

VLAN 172 SVI (172.16.1.1/29) is configued on 7600 switch on the Metro ring.

Customer core switches connect to the Metro switches on VLAN 172 (ports G0/1-2)

Colm

Not sure i follow. Is vlan 172 meant to be the same vlan in each site ? If so you can't use L3 etherchannels, they would have to be L2 etherchannels. If you use L3 etherchannels each site would need it's own IP subnet for the L3 etherchannel and there would not be a shared vlan between sites.

Jon

New Member

Re: Network Design - L3 Port-channels

Hi Jon,

Thanks for the reply. ISP is providing a layer 2 circuit (VLAN 172) around the ring.

Planning to configure each site with L3 port-channel 1 as shown below. Will Site-A (172.16.1.2) be able to ping Site-B (172.16.1.3)??

Will this solution work?

### Site-A ###

int port-channel 1

no switchport

ip address 172.16.1.2 255.255.255.224

int G0/1-2

no switchport

channel-group 1 mode on

### Site-B ###

int port-channel 1

no switchport

ip address 172.16.1.3 255.255.255.224

int G0/1-2

no switchport

channel-group 1 mode on

Hall of Fame Super Blue

Re: Network Design - L3 Port-channels

colmgrier wrote:

Hi Jon,

Thanks for the reply. ISP is providing a layer 2 circuit (VLAN 172) around the ring.

Planning to configure each site with L3 port-channel 1 as shown below. Will Site-A (172.16.1.2) be able to ping Site-B (172.16.1.3)??

Will this solution work?


Colm

An etherchannel is a p2p link between 2 switches. So you end up with 3 etherchannels ie. -

site A 6500 -> ISP metro switch A

site B 6500 -> ISP metro switch B

site C 3750 -> ISP metro switch C


if you want these etherchannels to all be in vlan 172 then you cannot use L3 etherchannels because each L3 etherchannel would need to be in it's own IP subnet ie. you cannot use a common subnet, in your case 172.16.1.0 255.255.255.224 for 3 L3 etherchannels. So in short no, your solution as configured would not work.

What you do is configure L2 etherchannels ie.

### Site-A ###

int port-channel

switchport mode access

switchport access vlan 172

int G0/1-2

switchport mode access

switchport access vlan 172

channel-group 1 mode on

int vlan 172

ip address 172.16.1.2 255.255.255.224

### Site-B ###

int port-channel

switchport mode access

switchport access vlan 172

int G0/1-2

switchport mode access

switchport access vlan 172

channel-group 1 mode on

int vlan 172

ip address 172.16.1.3 255.255.255.224

### Site-C ###

int port-channel

switchport mode access

switchport access vlan 172

int G0/1-2

switchport mode access

switchport access vlan 172

channel-group 1 mode on

int vlan 172

ip address 172.16.1.4 255.255.255.224

Jon

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