in your travels have you ever run into the gigastack, and its relation to STP?
the question came up a short time ago. The Cisco gigastack documentation does not cover STP - only how gigastack works. essentially, using daisy chained gigastack connections, one can connect up to 9 switches. If I understand correctly, the Cisco electronics and switch OS consider this stack a single entity for management purposes - i.e. can be managed from a single IP address. However, Cisco does not say one way or another if the electronics and the switch OS treat this stack as a single device for STP purposes. I'm guessing, based on this and other discussions that it would have to be a single device for STP purposes. It just would be nice if Cisco would provide the specific information. That brings up the corollary question - if you have on two switches gigastacked, then how does STP come into play. In a configuration such as this, again if I understand the documentation correctly, the electronics and the switch OS behave differently. ""Leigh Anne Chisholm"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Actually, the 5-4-3 rule has everything to do with detecting collisions. > It's > a limiting factor of distance so that a collision will be detected within the > first 64 bytes of a frame's transmission (also known as Ethernet's minimum > frame size). It's preferable to detect a collision before the frame leaves > the buffer of the transmitting interface - so that retransmission can be > accomplished at the data link layer rather than left to upper layers. > > Several months ago, Priscilla and I debated the 7 switch rule. If you wanted > to search the archives for the entire thread, it was titled "What's the > diameter of your switched network? [7:17489]" and was discussed at the end of > August, 2001. Here's an excerpt from one of my posts regarding the 7 hop > limit: > > From other statements I've read (Cisco published material) and from the > original excerpt I published, I'd imagine that the placement of the root does > matter. > > "Part of this restriction is coming from the age field BPDU carry: > when a BPDU is propagated from the root bridge towards the leaves of the > tree, the age field is incremented each time it goes though a bridge. > Eventually, when the age field of a BPDU goes beyond max age, it is > discarded. Typically, this will occur if the root is too far away from some > bridges of the network. This issue will impact convergence of the spanning > tree." > > I'd think that if a bridge were to be the third bridge away from the root, > and > another switch was the third bridge on the far side of the root, I wouldn't > expect to see any problems with MaxAge because I can't see the root being too > far from some of the bridges in the network. Now if a bridge were to be the > seventh, I could see how that would impose a greater delay and possibly > negatively impact the MaxAge parameter. Now my question would be... does > this > really apply in today's networks or is this more of a limitation of > yesteryear's "software-based bridges"? > > And essentially, that's the conclusion Priscilla and I came to - that the 7 > hop radius doesn't really seem to apply to today's switched environments... > You might want to check with her again though - Priscilla just authored a new > book on troubleshooting campus networks and may updated her thinking. > > > -- Leigh Anne Chisholm (CCNP, CCDP) -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > > Steven A. Ridder > > Sent: Saturday, May 18, 2002 5:16 AM > > To: [EMAIL PROTECTED] > > Subject: Re: STP and 7 hops [7:44408] > > > > > > I believe the 5-4-3 rule is for repeaters, not switches. > > > > > > ""Brian Hill"" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Steven, > > > > > > The 7 hop limit is from the root bridge, as STP calculates the tree from > > the > > > root. Historically, I am not sure why it's 7, but Ethernet has a base hop > > > "limit" of 4 switches (5-4-3 rule), so it doesn't really matter so much. > > The > > > reason for the 4 hop limit in Ethernet is simple: For 10 Mb or full > duplex > > > 100 Mb connections, the limit is mostly to reduce noise from the > > > amplification of the signal as it passes through the switches/hubs, where > > as > > > in 100Mb half-duplex connections, it is mostly to keep the propogation > > delay > > > within specs. > > > > > > Hope this helps, > > > > > > Brian Hill > > > CCNP, CCDP, MCSE 2000 (Charter Member),MCSE+I (NT4.0), > > > MCSA (Charter Member), MCP+I, MCP(21), Inet+, Net+, A+ > > > Lead Technology Architect, TechTrain > > > Author: Cisco, The Complete Reference > > > http://www.alfageek.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44478&t=44408 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
