MacWindows: Spanning tree blamed for slow Mac DHCP, switch problem

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Last updated: August 27, 2009

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Slow Mac DHCP Assignments Through Switches: Spanning Tree Protocal Blamed

Slow network connection for OS X, but not OS 9

Wednesday, July 8, 2009

Roger reports a problem with slow DHCP assignments:

I have a problem since we installed Cisco 1 Gb switches at work that it takes 30-40 seconds to get an IP address from the DHCP on the network. We're using a Juniper device. Until I get a good address I can not access anything on the network or Internet, once this has been resolved then everything worked fine. The OS X machines on the network are using 10.3.9 and 10.4.11. The OS 9 machines do not have this problem.

If you've seen this issue

Another reader reports OS X, Cisco problem

Monday, July 13, 2009

John Grubb responded to last week's report of a problem with Mac OS X connections to Cisco hardware:

Yes. Mac OS X seems to continually degrade on its connection to Cisco switches and routers. I suspect the configd file is part of the culprit, but have no proof.

If you've seen this

Suggestion for slow Mac DHCP with Cisco switches

Thursday, July 16, 2009

Jens Lodholm found some documentation that may fix problems with Macs with slow DHCP connections through Cisco switches:

In response to Roger's slow DHCP assignments on Cisco switches, here's a link with advice on altering settings on the Cisco gear. Scan for "Reduce Startup Delay."

If you've tried this

Spanning tree blamed for slow Mac DHCP, switch problem

Tuesday, July 21, 2009

Two readers report that the Spanning Tree Protocol used in Cisco and other switches is responsible for slow Mac DHCP assignments. Eric Stein reports:

Turn off spanning tree for the ports connected to Macs or insert dumb switches between the Macs and the dysfunctionally smart Cisco hardware.

John Lockwood in the United Kingdom says this is an old problem:

This suggested fix basically involves turning "Spanning Tree Protocol" off for the ports that Macs are connected to. Problems between Macs and Spanning Tree have existed for many, many years and even pre-date Mac OS X. For example see this Apple article from 2003.

It does not merely apply to Cisco switches either, I had a relatively recent case that involved some NetGear managed Gigabit switches.

Comment below

Port host command for slow network connection for OS X Cisco switches

Thursday, August 27, 2009

Rich Dagel has another suggestion for the problem of slow Mac DHCP assignments through Cisco switches:

Use to have the same issue. Check the portfast. Also, a big one for us was port host command. It would sometimes take up to 60 seconds for a Mac to get an IP address before we used the port host command.

We've previously reported other suggestions for this problem. If you have one

Comment below

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