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Configuring FastEtherchannel

I have a Catalyst 5500 and a Catalyst 2900XL. The 2900XL is linked from ports f0/23 and f0/24 to 5500 ports 3/3 and 3/4. Assuming that all the duplex, speed, and VLAN settings are the same on all four ports, should the configuration be like below?

5500

switch(enable) set port channel 3/3 mode on

switch(enable) set port channel 3/4 mode on

Do I need to add the two ports to an admin group first?

Also, can somebody help me with the config on the 2900XL using IOS 12.0?

Thanks for your time

Daniel,

8 REPLIES

Re: Configuring FastEtherchannel

Daniel,

Firstly can the H/W support etherchannel, depending on OS running you can issue a sh port cap 3/3 and sh port cap 3/4. This will tell you if the H/W is capable.

Also i have in the past had problem creating a channel with last two ports in the EBC, the EBC is grouped into ports of 4, and if you have no channel omn the 1st two then it would not channel on the second.

i found a DOC to prove the above theory:

EtherChannel port bundle must consist of two or four contiguous ports on the same module. The ports in an EtherChannel must belong to the same port group (ports that share the same EtherChannel controller).

NB!!!! Depending on the hardware, there might be additional restrictions. For example, on certain modules, you cannot form an EtherChannel with the last two ports in a port group unless the first two ports in the group already form an EtherChannel with the exception of the module (WS-X5010) then an EtherChannel bundle can consist of any two to eight ports on the module. Ports in an EtherChannel do not have to be contiguous.

As for the 2900XL, it all depends on what you are trying to do. If it's the Etherchannel then make sure you make them trunks and switchports then pile them into a common group.

Eg: Ports config'd for channel 1

interface FastEthernet0/1

port group 1

switchport trunk encapsulation dot1q

switchport mode trunk

!

interface FastEthernet0/2

port group 1

switchport trunk encapsulation dot1q

switchport mode trunk

!

interface FastEthernet0/3

port group 1

switchport trunk encapsulation dot1q

switchport mode trunk

!

interface FastEthernet0/4

port group 1

switchport trunk encapsulation dot1q

switchport mode trunk

New Member

Re: Configuring FastEtherchannel

This is what I get when I issue show po cap 3/3 - does this appear to support FastEtherchannel?

BK-CAT5500 (enable) sh po cap 3/3

Model WS-X5201R

Port 3/3

Type 100BaseFX MM

Speed 100

Duplex half,full

Trunk encap type 802.1Q,ISL

Trunk mode on,off,desirable,auto,nonegotiate

Channel 3/3-4,3/1-4

Broadcast suppression percentage(0-100)

Flow control receive-(off,on),send-(off,on)

Security yes

Membership static,dynamic

Fast start yes

Rewrite yes

New Member

Re: Configuring FastEtherchannel

Ok, I assume ports 3/1-4 are one EBC. If that is the case then 3/1 and 3/2 need to be part of one Etherchannel and 3/3 and 3/4 need to be part of another Etherchannel.

Can you help me with the actual commands I will need to enter on the 5500 and 2900 to form the Etherchannel

best regards,

Re: Configuring FastEtherchannel

You should have the stuff on the 2900 i posted. Just make sure that the speeds and basic stuff matches and that all VLAN's allowed across the trunks are the same on both sides, this is important.

For the 5500:

set trunk 3/1 des 1-1005 dot1q

set trunk 3/2 des 1-1005 dot1q

set port channel 3/1-2 auto ( if this does not form a channel use ON). This just helps PaGP.

For 2900:

interface FastEthernet0/23

port group 1

switchport trunk encapsulation dot1q

switchport mode trunk

!

interface FastEthernet0/24

port group 1

switchport trunk encapsulation dot1q

switchport mode trunk

New Member

Re: Configuring FastEtherchannel

All my trunks are currently set to isl, will they need to be changed to dot1q?

Daniel,

Re: Configuring FastEtherchannel

Daniel,

You do not have to change at all, however just a note:

ISL is Cisco Specific and has more overhead in terms of bytes per frame than dot1q. So at the end of the day to stick with Standards and "vendor interop" i would move to dot1q for better QoS mapping etc and also There is no ISL on GIG to the best of my knowledge.

Also Cisco has included 802.1w/s which allows Multiple Spanning Tree instances over a dot1 trunk, the original IEEE doc stated that 802.1 device runs only a single SPT instance for all VLAN's, this has been modified by 802.1s.

New Member

Re: Configuring FastEtherchannel

According to a Cisco doc I have read, you must disable the 5500 port whilst configuring FEC. This is so that Spanning Tree does not form a loop. I have configured FEC on my access layer switches, and can I now go ahead and configure FEC on 5500? I recieved a lot of MLS errors when I configured the port groups on the access layer switch, plus the link went down for 5 minutes. Is this normal?

Daniel,

New Member

Re: Configuring FastEtherchannel

When I configured FEC on the access layer device, all the existing config (STP, VLANS, Trunking info etc) was changed on the two uplink ports to be identical. Is this normal?

Daniel,

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