cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
Announcements

Community Helping Community

828
Views
4
Helpful
3
Replies
Highlighted
Enthusiast

Connecting heterogenous switching

I have a 3750 Cisco switch. I connected it to a bunch of Onenet switches that are in a daisy-chain topology.

Since I don't have management over the Onenet switches, the 3750 interface - that connects to Onenet- is put in vlan access mode:

3750Sw#sh run int fa1/0/48

Building configuration...

Current configuration : 232 bytes

!

interface FastEthernet1/0/48

description --- uplink access vers Onenet switches ---

switchport access vlan 1100

switchport mode access

no keepalive

priority-queue out

mls qos trust cos

spanning-tree bpdufilter enable

end

The reason behind "no keepalive" is that the 3750 keeps on sending keepalives and does not receive any from Onenet. This leads to a "loop" syslog message and the port is err-disabled.

What are the drawbacks of this design? Is there any better?

Thanks

1 ACCEPTED SOLUTION

Accepted Solutions
Enthusiast

Re: Connecting heterogenous switching

Well I guess that depends on the switch. I ran into some Planet switches that didn't, and I don't think some of these small unamanaged desktop switches that you can buy over the counter do. Most other "modern" network switches do of course.

View solution in original post

3 REPLIES 3
Enthusiast

Re: Connecting heterogenous switching

Loopback error

A loopback error occurs when the keepalive packet is looped back to the port that sent the keepalive. The switch sends keepalives out all the interfaces by default. A device can loop the packets back to the source interface, which usually occurs because there is a logical loop in the network that the spanning tree has not blocked. The source interface receives the keepalive packet that it sent out, and the switch disables the interface (errdisable). This message occurs because the keepalive packet is looped back to the port that sent the keepalive:

%PM-4-ERR_DISABLE: loopback error detected on Gi4/1, putting Gi4/1 in
err-disable state

Keepalives are sent on all interfaces by default in Cisco IOS Software Release 12.1EA-based software. In Cisco IOS Software Release 12.2SE-based software and later, keepalives are not sent by default on fiber and uplink interfaces. For more information, refer to Cisco bug ID CSCea46385 (registered customers only) .

The suggested workaround is to disable keepalives and upgrade to Cisco IOS Software Release 12.2SE or later.

Ref:

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00806cd87b.shtml

But it might be an idea to make sure you don't have any loops in the network. Maybe in those onenet switches there are two cables between a couple of switches, or they don't support SPT?? or something. Would be a good idea to check that. What you have done is apply a workaround, which is fine, but it would be good to find the route cause and resolve that.

HTH,

Ian

Enthusiast

Re: Connecting heterogenous switching

Ian,

Our 3750 IOS version is 12.2(50)SE1. Yet it sends keepalives.

iwhitmore wrote:

Maybe in those onenet switches there are two cables between a couple of switches, or they don't support SPT??

Are there switches that do not support STP? I thought that all switches out in the market do support it.

We don't have support over the Onenet switches. They're black boxes for us

Enthusiast

Re: Connecting heterogenous switching

Well I guess that depends on the switch. I ran into some Planet switches that didn't, and I don't think some of these small unamanaged desktop switches that you can buy over the counter do. Most other "modern" network switches do of course.

View solution in original post

CreatePlease to create content
Content for Community-Ad