Good to see you use Netpro a lot.. this is the best place to be in !!!
Trunks are used to carry traffic that belongs to multiple VLANs between devices over the same link. A device can determine which VLAN the traffic belongs to by its VLAN identifier. The VLAN identifier is a tag that is encapsulated with the data. ISL and 802.1Q are two types of encapsulation that are used to carry data from multiple VLANs over trunk links.
Anyway, ISL is a trunking protocol, which will tag all the VLANs flowing through two switches... ISL is a Cisco proprietary protocol for the interconnection of multiple switches and maintenance of VLAN information as traffic goes between switches. ISL provides VLAN trunking capabilities while it maintains full wire-speed performance on Ethernet links in full-duplex or half-duplex mode. These useful info is been taken from the following URL:
Please be aware that ISL is a CISCO proprietary protocol and that it has been superceded by the IEEE 802.1Q standard. Cisco is recommending the use of .1q and there are cisco products now that support .1q but not ISL. So, unless you have legacy cisco equipment that support only ISL, stay away from it.
If interoperability with other manufacturer switches is a concern, you must use .1q.
DEAR ahmednaas! Coukld you plz give me some evidence about what u said" Cisco is recommending the use of .1q and there are cisco products now that support .1q but not ISL" i want to make further Discussion with my Seniors!!!
There is no document the states explicitly that cisco recommends .1q. I came to this conclusion from discussions with cisco employees and others. The main argument is of course interoperability with non-cisco equipment.
If I recall correctly, the 2950/2960 series of switches does not support isl.
As a general practice, network consultants/design people, normally recommend dot1q as the trunking protocol, since it is an open standard, as other said... but it all depends on your company's requirement and security standards.. Just remember that ISL is not supported on the following switches, as ahmed was mentioning:
4) Cat 500
Otherwise, there are some few differences.. ISL supports upto 1000 VLANs and dot1x upto 4096 VLANs.... ISL normally uses Per VLAN spanning tree (PVST), which offers great flexibility & load balancing..dot1q normally works on Mono spanning tree (MST), but is enhanced now to work with PVST+ for flexibiligy and load balancing.... So, if you see all the pro's , it is always good to use dot1q than ISL.... You can point out these points to your seniors.. also have a look at the following URL, for frame formats of ISL and dot1q:
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.