03-21-2002 05:41 AM - edited 03-01-2019 08:58 PM
Hello,
My question is about the nature of inverse arp:
I've seen that if I configure a meshed Frame relay Networks with subinterfaces (point-to-point but also multipoint), if the inverse ARP is not activated, to permit the routing update of a routing protocol, I've had to set up the keyword "broadcast" at the end of the "frame relay map" commands.
If instead the inverse arp is active the command "frame relay map" is useless, I've only specified the "frame realy DLCI" on the sub interfaces, and the routing protocol work well, without that I add the keyword "broadcast" from no part. My question is:
IF the inverse arp is active, broadcast is permitted
by default?
and again, the inverse arp notifications is a broadcast itself?
thank's very much in advance.
Graziano
03-21-2002 06:38 AM
These are really separate issues.
inverse arp is the mechanism that allows a router to discover the IP address on the other side of a point-to-mulitpoint frame PVC and associate that IP address with that PVC. Frame-relay map is the mechanism to configure this manually. They are mutually exclusive.
broadcast only applies to point-to-mulipoint configurations. point-to-point sub-interfaces don't need to broadcast as such since there is only one other host to send data to.
broadcast needs to be enabled on point-to-multipoint configurations if broadcast or multicast packets need to go over the frame. If you're using RIP or OSPF, for instance, and choose not to use the neighbor statements, broadcast will need to be enabled.
Mick.
03-21-2002 08:14 AM
Hi Mick,
thank you very much for the answer, I've understood but...
Look this example, a router with a subinterface multipoint with the inverse arp is enabled:
-----------------------------------------------
interface FastEthernet0/0
ip address 10.11.11.250 255.255.255.0
duplex auto
speed auto
!
interface Serial0/0
no ip address
encapsulation frame-relay
frame-relay lmi-type ansi
!
interface Serial0/0.1 multipoint
ip address 172.16.0.2 255.255.255.0
frame-relay interface-dlci 704
frame-relay interface-dlci 709
router eigrp 1234
passive-interface FastEthernet0/0
network 10.0.0.0
network 172.16.0.0
no auto-summary
no eigrp log-neighbor-changes
-------------------------------------------------
Can you explane me why this configuration work well without the keyword "broadcast" at the frame relay-dlci command level?
thank's,
Graz
03-21-2002 08:45 AM
You shouldn't be using Frame-relay interface-dlci on a multipoint interface. Its redundant. Use either inverse arp or frame map. interface-dlci is used to map a PVC to a point-to-point sub-interface.
Mick.
03-22-2002 12:18 AM
Hi Mick,
really, I've tryed in lab that, if I work with inverse arp, if I've a multipoint subinterface with
3 dlci I must specifie this, because the FR switch
doesn't know the subinterface itself.
If I don't write the FR dlci command the network doesn't work... then I don't think that it is redundant... what do you think about?
PS: sorry for my very bad english...
rgds,
Graz
03-22-2002 05:22 AM
You are correct.
If you're using multiple point-to-multipoint subinterfaces, and you wish to use inverse-arp, you need to associate the DLCI with the appropriate subinterface. My mistake.
Guess I'm outa practice on reading questions lately. :-/
Mick.
03-22-2002 07:10 AM
Well,
thank you very much Mick!
rgds,
Graz.
03-21-2002 06:42 AM
Hi.
You asked: "IF the inverse arp is active, broadcast is permitted by default? "
Answer: YES. You can check with the "show frame-relay map" command.
Regarding the Inverse ARP notifications being a broadcast itself... I'm not sure, but I do think so (at the IP layer of course).
Rgds.
NM
03-21-2002 08:16 AM
Hi Nuno,
Thank's very much for the answer, perfect!
Bye,
Graz.
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide