From: Chris Lewis \(chrlewis\) (chrlewis@cisco.com)
Date: Thu Jun 30 2005 - 12:36:45 GMT-3
Let me summarize the requirements, so that I am sure I am trying to
answer the right question.
1. Encapsulation must allow multiple protocols
2. No inarp is allowed
3. No map commands allowed
For one, I would read it as you have, in that the question is meaning
the encapsulation needs to be set to one that allows multiple protocols
to use the same PVC, which is snap.
For two, I would say (as do you) that when a static mapping is created,
inarp is disabled. I do not think that the router is trying to use inarp
for other protocols that snap could support. You do not enable those
protocols until you specify a protocol address, like an IPX, or IPv6
address on the ATM interface. Without enabling them, you cannot perform
inarp for them.
Now the question of the meaning for what you are seeing in the output.
If you look at the documentation for the encapsulation command, you will
see this for aal5snap "AAL and encapsulation type that supports Inverse
ARP" this says to me that other encapsulations do not support it. You
will see inARP disabled for aal5mux encap whether or not you have a
protocol mapping configured. I believe the inARP entry in the show atm
vc detail command for the all5snap encapsulation does not indicate inARP
is active, it is just saying that if activated, this is the timer it
would use.
The way to prove this is use deb atm arp, log to the buffer and see that
your router is in fact not sending any arp packets, then take the static
mapping off and see that it is.
When you have inarp enabled (by not configuring a static map and using
inarp 1 to speed up operation of the PVC), this debug shows output like
"Sending first PVC INARP for 20/113"
When you configure static mapping, those packets are no longer sent
out.
For three, it is asking you to use the pvc command (as you have) and not
use the legacy map-group/map-list commands as follows:
interface ATM1/0.1 multipoint
ip address 172.16.1.1 255.255.255.0
map-group IP
atm pvc 11 0 100 aal5snap
!
map-list IP
ip 172.16.1.2 atm-vc 11 broadcast
In your configurations you have chosen to use a vc-class and apply that
to the interface with the class-int command. This may or may not work
depending on what else has to be configured. If you want to apply a
class configuration to a VC (as I think you do given the naming of the
class as PVC32), it is more specific to use class-vc under the pvc
configuration as below:
interface atm 4/0.5 multipoint
pvc 0/56
class-vc PVC32
The way you did it, the class would apply to all PVCs, which may not be
what you want.
Much simpler is to specify these parameters directly under the PVC
command as follows:
Int atm 1/0
Pvc 20/32
encapsulation aal5snap
ubr+ 3072 512
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Gustavo Novais
Sent: Saturday, June 25, 2005 2:16 PM
To: Cisco certification
Subject: InArp and Encapsulation aal5snap / aal5mux
Hello
this is my first mail to GS since I've started studying to the LAB,so if
I'm posing a dumb question, I'm sorry but a newbie is a newbie... :)
I have two doubts and I wonder if the GS could clarify it to me.
I'm doing some exercises regarding ATM on which it is mentioned that "no
inarp is allowed and that the encapsulation type to be used is the one
which allows multiple protocols to be used."
To me they are talking about aal5snap, which is fine.
After that I do a static mapping of the IP address on the remote side,
which should disable inarp. So why, when I do sh atm vc detail there is
always one field who is telling me InArp frequency 15 minutes, if it
should be off?
On the opposite side, when using aal5mux (one protocol only) it tells me
InArp disabled, as it should after a static mapping.
In order to disable inarp on aal5snap do I need to do static mappings to
ALL protocols suported on aal5snap?
!
vc-class atm PVC32
ubr+ 3072 512
encapsulation aal5snap
!
interface ATM1/0.32 multipoint
ip address 150.50.6.6 255.255.255.128
class-int PVC32
pvc 0/32
protocol ip 150.50.6.9 broadcast
!
R6#sh atm vc detail
ATM1/0.32: VCD: 5, VPI: 0, VCI: 32
UBR+, PeakRate: 3072, Minimum Guaranteed Rate: 512
AAL5-LLC/SNAP, etype:0x0, Flags: 0x20, VCmode: 0x0 OAM frequency: 0
second(s) InARP frequency: 15 minutes(s) Transmit priority 3
InPkts: 1068, OutPkts: 1093, InBytes: 77047, OutBytes: 78609
InPRoc: 1068, OutPRoc: 28, Broadcasts: 1065
InFast: 0, OutFast: 0, InAS: 0, OutAS: 0
InPktDrops: 0, OutPktDrops: 0/0/0 (holdq/outputq/total)
CrcErrors: 0, SarTimeOuts: 0, OverSizedSDUs: 0, LengthViolation: 0,
CPIErrors: 0
Out CLP=1 Pkts: 0
OAM cells received: 0
OAM cells sent: 0
Status: UP
The other doubt is when it is refered to configure a PVC using map
commands, to what are they referring? Is it "atm pvc VCD VPI VCI
encapsul ..." 'Cause I can't find any map command related to ATM... :(
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