[Dibbler] multiple Cisco relays to Dibbler server

Tomasz Mrugalski thomson at klub.com.pl
Sun Nov 29 12:25:04 CET 2009

On Sat, 28 Nov 2009 somebody known as Karl Auer wrote:

> I found this in a Cisco doc:
>   "The Interface-Identifier DHCPv6 Option added to the DHCPv6 relayed
>    message is formed by the interface name concatenated with the VLAN
>    Identifier when available. This way the value of the
>    Interface-Identifier Option is persistent after a router reload."
> But there is other information suggesting that it is just the interface
> name. Either way it's a bit limited, as one might well have several
> routers with the same interface names and VLANs...
That is true. Unfortunately, my world domination plan didn't reach Cisco 
aquisition phase yet. Due to lack of access to Cisco source code I'm 
afraid I cannot help you at this time :)

Seriously, I've reread RFC3315 and there is nothing that says that 
interface-id must be globally unique. I think Cisco implementation is 
RFC3315 compliant, but in this case it would be better if you could 
configure relay with explicit interface-id value (just as you can do in 
Dibbler relay).

You mentioned that Cisco docs as a bit confusing regarding content of the 
interface-id value. The easiest way will be to use Wireshark to capture 
the traffic, see the option's content yourself and get definite answer.


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