I think so - it's an encapsulation issue. http://www.cisco.com/warp/public/473/741_4.html
"ISL is a Cisco proprietary protocol for interconnecting multiple switches and maintaining VLAN information as traffic goes between switches. ISL provides VLAN capabilities while maintaining full wire speed performance on Ethernet links in full-duplex or half-duplex mode. ISL operates in a point-to-point environment and will support up to 1000 VLANs. ISL and 802.1q are two types of encapsulations used to carry VLAN information over a trunk link. In ISL, the original packet is encapsulated and an additional header is added before the frame is carried over a trunk link. At the receiving end, the header is removed and the packet is forwarded to the assigned VLAN. In 802.1q, the trunking device inserts a four-byte tag into the original packet and recomputes the Frame Check Sequence (FCS) before sending the frame over the trunk link. At the receiving end, the tag is removed and the packet is forwarded to the assigned VLAN." -----Burton -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Blake Sent: Tuesday, February 25, 2003 11:45 PM To: [EMAIL PROTECTED] Subject: RE: [Ntop] Monitoring a router trunk port hmmm ... ok I will have to test NTOP monitoring a 802.1q trunk. I guess they are 2 different animals because 802.1q uses a internal tag and ISL uses an external tag, which Im assuming is why the ISL traffic will be classified as non-ip other traffic ... makes sense. thanks, Blake --- "Burton M. Strauss III" <[EMAIL PROTECTED]> wrote: > I don't think there's any support for ISL. The > support I'm aware of is for > 802.1q. Which isn't to say that ISL couldn't be > added ... > > Try doing a couple of tcpdump or ethereal traces on > the link. See what you > see. But based on what I read this weekend about > ISL encapsulation, ntop > should treat it as non-IP other traffic. > > -----Burton > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Blake > Sent: Tuesday, February 25, 2003 2:39 PM > To: [EMAIL PROTECTED] > Subject: [Ntop] Monitoring a router trunk port > > > > Hi, does it make sense to monitor the interface of a > router which is configured as a ISL trunk port > routing > between multiple VLANs? > > The other option is to have a NIC for each VLAN I > want > to monitor with NTOP and was wondering if I could > just > monitor the trunk port of the router. I guess Im > wondering what exactly NTOP would see and this may > be > more of a networking thing I will have to read up on > but was just wondering if there was functionality > built in NTOP that would enable NTOP to function on > a > trunk port. > > I do not currently have this setup to test so that > is > why I ask ... Im just planning ahead :) > > Any thoughts would be appreciated. Thanks in > advance! > > --Blake > > > __________________________________________________ > Do you Yahoo!? > Yahoo! Tax Center - forms, calculators, tips, more > http://taxes.yahoo.com/ > _______________________________________________ > Ntop mailing list > [EMAIL PROTECTED] > http://listgateway.unipi.it/mailman/listinfo/ntop > > _______________________________________________ > Ntop mailing list > [EMAIL PROTECTED] > http://listgateway.unipi.it/mailman/listinfo/ntop __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - forms, calculators, tips, more http://taxes.yahoo.com/ _______________________________________________ Ntop mailing list [EMAIL PROTECTED] http://listgateway.unipi.it/mailman/listinfo/ntop _______________________________________________ Ntop mailing list [EMAIL PROTECTED] http://listgateway.unipi.it/mailman/listinfo/ntop
