I came across an odd issue yesterday that I wanted to address. My customer complained about slow DHCP times on the Brocade equipment. He said that on his Cisco gear, it only takes about a second or so to get DHCP. On the Brocade, it takes up to 30 seconds or so. It was consistent on all Brocades, and the same on the Cisco gear. So what I found was that spanning-tree was causing this. On the default vlan, spanning-tree was enabled and when I went to disable this, it cleared up the DHCP issue. I was then able to get DHCP in the same amount of time as the Cisco gear. I found this odd, and I have not researched this yet to see what the issue really is, but we can at least know what the fix is. And in this case, Im ok with spanning-tree not being enabled.
switch(config)#no spanning-tree
switch(config)#wr mem
I dont usually recommend turning spanning-tree off. But in this case, I did to obtain the customer goal.
Yep, have this issue as well. It's related to STP, and even using RSTP it's still here. We've created a case with Brocade about this.
ReplyDeleteThanks for your comment. If you get any resolution as to why this happened, Id like to hear about it. Thanks again.
Deletei have spanning tree set to port fast and haven't seen this. I had the same thing happen when i switched to dell switches some years ago, spanning-tree was on. set it to port-fast and all was well. so i set our 6450's to port fast and haven't seen the lag issue.
ReplyDeleteI though it was by design, set edge ports to port-fast in they are station connected.
I thought that the brocades had portfast enabled by default. Either way, good information. Thanks.
DeleteThe delay might be due to STP. So when we disable it, blocking and discarding is removed and the switchport stays in forwarding state. This will help to access the DHCP faster.
ReplyDeleteThis is the only reason I could think of.