From: John Spencer (johnspencer@xxxxxxxxx)
Date: Wed Feb 06 2002 - 14:42:39 GMT-3
Greetings,
Sorry I dont have routers at home and therefore can not show you any output
examples. But the point is that I can confirm the issues mentioned in Mr
Caslows book and others of a similar nature of the dynamic mappings being
"lost" (also on 12 code and onwards)
Personally I would not rely on inarp in a production environment. If you
have a simple architecture you may be ok, but why take the risk.
Here is all the info anyone should need:-
http://www.cisco.com/warp/public/125/13.html
Also how inarp works is a matter of an RFC standard
ftp://ftp.isi.edu/in-notes/rfc2390.txt
Regards
John Spencer
----- Original Message -----
From: "Przemyslaw Karwasiecki" <karwas@ifxcorp.com>
To: "Jason Gardiner" <gardiner@sprint.net>
Cc: "JOSE ANGEL MARTINEZ DE LA VARA" <jamartinez@landata.payma.es>;
"Muhamamd Durrani" <dan_schaw@yahoo.com>; <ccielab@groupstudy.com>
Sent: Wednesday, February 06, 2002 5:37 PM
Subject: Re: Frame Relay Map Vs Inverse Arp !
> Can you please tell us what IOS you are using?
>
> Look, from my previous posting:
>
> The only (protocol,DLCI) is (IP,201).
> There is static map there (to 10.10.1.3).
> It doesnt prevent dynamic map for 10.10.1.1
>
> The only possibility is, (as pointed by Jaeheon Yoo tonight),
> that this map is created when "far end" is doing inverse arp.
>
> I will investigate it later.
>
> Thanks,
>
> Przemek
>
> > > r2#sh fram map
> > > > Serial0 (up): ip 10.10.1.1 dlci 201(0xC9,0x3090), dynamic,
> > > > broadcast,, status defined, active
> > > > Serial0 (up): ip 10.10.1.3 dlci 201(0xC9,0x3090), static,
> > > > CISCO, status defined, active
> > > > r2#reload
> > > > Proceed with reload? [confirm]
> > > >
> > > > 19:02:16: %SYS-5-RELOAD: Reload requested
> > > >
> > > > After reload:
> > > > r2#sh fram map
> > > > Serial0 (up): ip 10.10.1.1 dlci 201(0xC9,0x3090), dynamic,
> > > > broadcast,, status defined, active
> > > > Serial0 (up): ip 10.10.1.3 dlci 201(0xC9,0x3090), static,
> > > > CISCO, status defined, active
> > > >
>
> On Wed, 2002-02-06 at 11:30, Jason Gardiner wrote:
> > Static maps only disable inverse-arp for the protocol and dlci spcified
in
> > the map:
> >
> > Tod#sh fram map
> > Serial0/0 (up): ip 10.10.10.1 dlci 201(0xC9,0x3090), dynamic,
> > broadcast,, status defined, active
> > Serial0/0 (up): ip 10.10.10.5 dlci 203(0xCB,0x30B0), dynamic,
> > broadcast,, status defined, active
> > Serial0/0 (up): ip 172.16.1.1 dlci 201(0xC9,0x3090), dynamic,
> > broadcast,, status defined, active
> >
> >
> > Notice that all DLCIs are mapped through inverse-arp, as shown by the
> > 'dynamic' keyword. Now, I'll set up a static map on DLCI 201:
> >
> > Tod#conf t
> > Enter configuration commands, one per line. End with CNTL/Z.
> > Tod(config)#int s0/0
> > Tod(config-if)#fram
> > Tod(config-if)#frame-relay map ip 10.10.10.2 201 broad
> > Tod(config-if)#end
> > 6w5d: %SYS-5-CONFIG_I: Configured from console by console
> >
> >
> > And clear the inverse-arp map:
> >
> > Tod#clear frame-relay-inarp
> >
> >
> > Wait several minutes:
> >
> > Tod#sh fram map
> >
> > Serial0/0 (up): ip 10.10.10.2 dlci 201(0xC9,0x3090), static,
> > broadcast,
> > CISCO, status defined, active
> > Serial0/0 (up): ip 10.10.10.5 dlci 203(0xCB,0x30B0), dynamic,
> > broadcast,, status defined, active
> >
> >
> > And you can see, the dynamic mappings to 201 are no longer present.
> >
> >
> >
> >
> >
> > On Wednesday 06 February 2002 10:44, Przemyslaw Karwasiecki wrote:
> > > I am leaning more and more toward conclusion that statement
> > > in Caslow, about side effect of static maps disabling dynamic
> > > inverse arp is not correct.
> > > At last not in IOS 12.1.12a
> > >
> > > About race condition:
> > > I was just desperatly trying to find out some logical explanation
> > > which will be consistent with Caslow statement.
> > > This also explain why I was doing reload instead "clear ..."
> > > Caslow mentioned reload, so I was blindly doing reload.
> > >
> > > Anyway -- thank you very much about excellent explanation
> > > that interface after power on is in shutdown state, so any
> > > race conditions are very unlikly, (if not impossible -- no shutdown
> > > is parsed as last interface parameter)
> > >
> > > ---
> > > Bottom line:
> > > Unless I am explicitely asked for configuration without
> > > frame-relay maps, i will put them, just not to take a risk that
> > > this 11.3 I have never tested in my lab is "Caslow compliant" :-)
> > >
> > > Thanks,
> > >
> > > Przemek
> > >
> > > On Wed, 2002-02-06 at 04:18, JOSE ANGEL MARTINEZ DE LA VARA wrote:
> > > > Hi,
> > > >
> > > > I think in that statement Caslow is wrong. Also in my lab Inarp is
> > > > running when using maps, and that really makes sense. Think about
your
> > > > hub-and-spoke topology, the hub can use inverse arp to get all
addresses,
> > > > but the spokes cannot. You have to configure the map statements to
the
> > > > other spokes, but how can the router know that those statements are
to
> > > > the spokes and the hub or just the spoke, or none of them? I think
it is
> > > > better the way it si because it is your active decision to disable
inarp
> > > > when you know there are the right maps configured as static.
> > > >
> > > > Perhaps in the past enabling maps could disable inarp, but that's
not
> > > > very fair and Cisco guys could have changed it in 12.1.
> > > >
> > > > About race betwen config parser and inverse arp ... as you know
inverse
> > > > arp runs over frame relay, and by default and before config parsing
there
> > > > is hdlc on every interface and all are shutdown. When the config
parser
> > > > gets to the interface and selects encapsulation frame relay it
> > > > inmediately gets the map command so I think there is not eneugh time
for
> > > > the inarp message to be sent or even for an lmi to be received,
don't you
> > > > think so? And another thing: why don't you erase the frame relay
maps
> > > > table with 'clear frame-relay-inarp' command instead of reloading?
There
> > > > will be no races at all with the config parser.
> > > >
> > > > Good luck with your tests and please tell us your conclusions.
> > > >
> > > > Jose Angel
> > > >
> > > > -----Mensaje original-----
> > > > De: Przemyslaw Karwasiecki [mailto:karwas@ifxcorp.com]
> > > > Enviado el: martes, 05 de febrero de 2002 23:20
> > > > Para: Muhamamd Durrani
> > > > Cc: ccielab@groupstudy.com
> > > > Asunto: Re: Frame Relay Map Vs Inverse Arp !
> > > >
> > > >
> > > > Hello,
> > > >
> > > > My understanding of this problem/phenomenon is as folow:
> > > > 1) you are assigning encapsulation and IP address
> > > > to serial interfaces on the spoke routers
> > > > 2) spoke router learn by inverse arp (enabled by default)
> > > > about IP address of a hub router and keeps this map
> > > > in nonpersistent (RAM) memory
> > > > 3) you create static map from spoke to another spoke
> > > > using as L2 address DLCI from your spoke to hub router
> > > > -- acording to Bruce Caslow book, this configuration
> > > > statement disables inverse arp on this particular DLCI.
> > > > But you alredy have, in nonpersistent memory, map from
> > > > your spoke to your hub.
> > > > 4) you save your config (normal, usual wr mem)
> > > > 5) you reload spoke router
> > > >
> > > > ---
> > > >
> > > > 6) before spoke router has opportunity to learn
> > > > via inverse arp maping between IP of your hub, and DLCI
> > > > to your hub, configuration statement with static map is
> > > > parsed, effectivelly stoping inverse arp on this DLCI.
> > > >
> > > > ---
> > > >
> > > > 7) Final effect
> > > > -- after reload your spoke cannot ping hub router.
> > > >
> > > > Now, to be technically correct, it is difficult to
> > > > answer your question, because there is no sentence
> > > > in your original post with question mark,
> > > > but if your confusion is comming from the simple fact
> > > > that router is performing dynamic inverse arp
> > > > even when static map is present (against Caslow p.118),
> > > > I have to tell you that I am confused as well.
> > > >
> > > > In my lab behaviour is exactly as in yours:
> > > >
> > > > Before reload:
> > > >
> > > > r2#sh fram map
> > > > Serial0 (up): ip 10.10.1.1 dlci 201(0xC9,0x3090), dynamic,
> > > > broadcast,, status defined, active
> > > > Serial0 (up): ip 10.10.1.3 dlci 201(0xC9,0x3090), static,
> > > > CISCO, status defined, active
> > > > r2#reload
> > > > Proceed with reload? [confirm]
> > > >
> > > > 19:02:16: %SYS-5-RELOAD: Reload requested
> > > >
> > > > After reload:
> > > > r2#sh fram map
> > > > Serial0 (up): ip 10.10.1.1 dlci 201(0xC9,0x3090), dynamic,
> > > > broadcast,, status defined, active
> > > > Serial0 (up): ip 10.10.1.3 dlci 201(0xC9,0x3090), static,
> > > > CISCO, status defined, active
> > > >
> > > > r2#sh run int s0
> > > > Building configuration...
> > > >
> > > > Current configuration : 120 bytes
> > > > !
> > > > interface Serial0
> > > > ip address 10.10.1.2 255.255.0.0
> > > > encapsulation frame-relay
> > > > frame-relay map ip 10.10.1.3 201
> > > > end
> > > >
> > > >
> > > > Any comments on this?
> > > > Is Caslow wrong in his statement that static frame relay map
> > > > disables inverse arp on this DLCI?
> > > > Or this is kind of race condition and inverse arp is faster
> > > > then config parser?
> > > >
> > > > Thanks for your feedback,
> > > >
> > > > Przemek
> > > >
> > > > On Tue, 2002-01-22 at 00:41, Muhamamd Durrani wrote:
> > > > > Hi All !!
> > > > >
> > > > > I am running hub and spoke scenario ...all are using
> > > > > physical interfaces and all PVC's are up !!!
> > > > >
> > > > > I am using map for spoke to see each other !!!
> > > > > and spokes are using inverse-Arp to resolve HUB ip
> > > > > with local DLCI
> > > > >
> > > > > According to bruce caslow !
> > > > > If Frame relay Map is configured for a particular
> > > > > protocol and particular DLCI ..Inverse ARP for that
> > > > > particular DLCI is disabled automatically !!!!
> > > > >
> > > > > condition:
> > > > > if we saved Map statement into startup config :
> > > > >
> > > > > Is there any specific command to save MAP statement to
> > > > > startup config !!!!!
> > > > >
> > > > > cause i write my config into NVRAm and reload my
> > > > > router my router still running Inverse Arp to resolve
> > > > > HUB ip !!!!
> > > > >
> > > > > Any clue !!! Am I missing something !!!
> > > > >
> > > > > Regards,
> > > > >
> > > > >
> > > > >
> > > > >
This archive was generated by hypermail 2.1.4 : Thu Jun 20 2002 - 13:46:13 GMT-3