From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Wed Jun 22 2005 - 20:21:31 GMT-3
Robbie,
It doesn't really matter which encapsulation you use as long as
it matches on both ends. SNAP is a multi-protocol encapsulation, while
MUX is a single protocol encapsulation. This means that if you are
running MUX you can't run IPv4 and IPX on the same circuit. However
when you run PPPoA using AAL5MUX *all* traffic looks like PPP from the
perspective of the layer 2 process. This means that while you can have
IPv4 and IPX on the virtual-template, the ATM process still only sees
PPP being encapsulated.
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
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> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> robbie
> Sent: Wednesday, June 22, 2005 6:10 PM
> To: Group Study
> Subject: Re: ppp over ATM
>
> (Brians or Scott, please correct me if I am wrong here)
>
> aal5mux is when you're doing PPP or another layer 2 protocol across a
> link, IIRC. aal5snap is just pure IP across ATM with SNAP as the
> higher-order layer 2 protocol, which is what you should be using for
> most point-to-point ATM network links where all of the VC
configuration
> is handled on the switch.
>
> Example:
>
> This is a point-to-point ATM configuration for a routed (read:
non-PPP)
> connection to a remote network
>
>
> #show run int atm 3/0.253
> Building configuration...
>
> Current configuration : 238 bytes
> !
> interface ATM3/0.253 point-to-point
> ip address 172.30.255.69 255.255.255.252
> no ip mroute-cache
> pvc 1/283
> protocol ip 172.30.255.70 no broadcast
> encapsulation aal5snap
> !
> end
>
> Notice that we're not using PPP, just pure SNAP across the link.
Here's
> another config, from a PPPoA link:
>
> #show run int atm 3/0.92
> Building configuration...
>
> Current configuration : 152 bytes
> !
> interface ATM3/0.92 point-to-point
> no ip mroute-cache
> pvc 1/123
> encapsulation aal5mux ppp Virtual-Template2
> !
> interface Virtual-Template2
> bandwidth 768
> ip unnumbered Loopback1
> no peer default ip address
> ppp authentication pap
> end
>
> While the above config doesn't really reflect this, you can configure
> your PPP options in much the same way you would if you had a dial-up
> client hitting this port. HTH
>
> Cheers,
> Robbie
>
> ccie2be wrote:
> > Hi guys,
> >
> > I just came across something interesting and a bit scary.
> >
> > I was configuring ppp over ATM and since I didn't remember exactly
every
> > command needed, I checked the Doc-CD.
> >
> > In the doc-cd, all the examples used the aal5mux encap, so that's
what I
> > did. Surprise, surprise. It didn't work.
> >
> > After checking the SG and the config of the remote router for this
task,
> I
> > saw that aal5snap encap was being used.
> >
> > Once I reconfigured my router with aal5snap encap, it worked like a
> charm.
> >
> > But, this leads me to a couple questions:
> >
> > 1. If we're not explicitly told which aal5 encap to use in
the
> lab,
> > is there a way to figure out which encap to use other than by trial
or
> > error?
> >
> > 2. The actual solution was like this:
> >
> > int atm0.201 p2p
> > pvc 0/201
> > encap aal5snap
> > protocol ppp virtual-template 1
> >
> >
> > I couldn't find any example like this on the Doc-CD. Does such an
> example
> > exist? IF so, where?
> >
> > 3. Based on my results, I assume the encap type must be the
same
> on
> > both sides. Is this true?
> >
> >
> > Any insight on this would be greatly appreciated.
> >
> > TIA, Tim
> >
> >
This archive was generated by hypermail 2.1.4 : Wed Jul 06 2005 - 14:43:42 GMT-3