From: Matt Holbert (mholbert@xxxxxxxxxxx)
Date: Thu Jul 06 2000 - 12:13:47 GMT-3
Some of you have sent me snippets of the CCIEbootcamp lab8 configuration.
Lab8 is what got me first thinking about this. The Lab8 DECNET over ISDN
configuration does NOT work from what I can tell. The BGP keepalives
between R1 and R6 keeps the ISDN up periodically, just enough to allow
periodic refreshes of the DECNET routing tables. Try it simply router to
router. IT DOES NOT WORK!
Let me go into detail why. I am on node 1.7, trying to decnet ping node
1.6. Assume we have a default route like such:
decnet route default 1.6 1 3
This tells the router to route all routes not in the table to 1.6. However,
if you look in the routing table, 1.6 is not specified. Because no route is
available, routing fails as depicted below.
R7#sh decnet route
Area Cost Hops Next Hop to Node Expires Prio
*1 0 0 (Local) -> 1.7
Node Cost Hops Next Hop to Node Expires Prio
*(Area) 0 0 (Local) -> 1.7
*1.7 0 0 (Local) -> 1.7
*DEFAULT* : 3 1 using next hop address of 1.6
R7#ping decnet 1.6
Type escape sequence to abort.
Sending 5, 100-byte DECnet echos to 1.6, timeout is 5 seconds:
Host unreachable+
Host unreachable+
Host unreachable+
Host unreachable+
Host unreachable+
Success rate is 0 percent (0/5)
R7#
If we change the default route to the interface instead of the address,
encapsulation fails as detailed below.
R7#sh decnet route
Area Cost Hops Next Hop to Node Expires Prio
*1 0 0 (Local) -> 1.7
Node Cost Hops Next Hop to Node Expires Prio
*(Area) 0 0 (Local) -> 1.7
*1.7 0 0 (Local) -> 1.7
*DEFAULT* : 3 1 out on interface BRI0,
R7#debug decnet events
DECnet packets (errors) debugging is on
R7#ping decnet 1.6
13:22:40: DNET: Encapsulation failed (3) for interface BRI0
13:22:40: DNET: Encapsulation failed (3) for interface BRI0
Type escape sequence to abort.
Sending 5, 100-byte DECnet echos to 1.6, timeout is 5 seconds:
13:22:42: DNET: BRI0 Discard packet, waiting for re-enable.
13:22:47: DNET: BRI0 Discard packet, waiting for re-enable.
13:22:52: DNET: BRI0 Discard packet, waiting for re-enable
13:22:54: DNET: Sending level 2 routing updates on interface Ethernet1
13:22:54: DNET: Sending level 2 routing updates on interface Serial1
13:22:54: DNET: Sending level 2 routing updates on interface BRI0
13:22:54: DNET: Encapsulation failed (4) for interface BRI0
13:22:55: DNET: Encapsulation failed (3) for interface BRI0
13:22:55: DNET: Encapsulation failed (3) for interface BRI0.
13:22:57: DNET: BRI0 Discard packet, waiting for re-enable.
13:23:02: DNET: BRI0 Discard packet, waiting for re-enable.
Success rate is 0 percent (0/5)
R7#
13:23:10: DNET: Encapsulation failed (3) for interface BRI0
If I bring up the line with another protocol, say IP, the pings are answered
as detailed below.
R7#sh decnet route
Area Cost Hops Next Hop to Node Expires Prio
*1 0 0 (Local) -> 1.7
Node Cost Hops Next Hop to Node Expires Prio
*(Area) 0 0 (Local) -> 1.7
*1.6 2 1 BRI0 -> 1.6 40 64 V
*1.7 0 0 (Local) -> 1.7
*1.8 3 2 BRI0 -> 1.6
*DEFAULT* : 3 1 out on interface BRI0,
R7#ping decnet 1.6
Type escape sequence to abort.
Sending 5, 100-byte DECnet echos to 1.6, timeout is 5 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/23/24 ms
R7#
This works because the decnet routing tables are refreshed when the ISDN
line comes up. Now the BRI is mapped to node 1.7. After the ISDN call
terminates and the DECNET routes timeout, the pings quit working.
Does anyone have any workarounds?
Matt
> -----Original Message-----
> From: Matt Holbert [mailto:mholbert@icscorp.com]
> Sent: Wednesday, July 05, 2000 5:41 PM
> To: CCIE Lab (E-mail)
> Subject: DECNET over ISDN
>
>
>
> Hey everybody,
>
> I am working on DECNET over ISDN. I have a serial connection
> between two
> routers and I want the ISDN to be used if the serial fails.
> My interesting
> traffic for the BRI is DECNET only, not DECNET routing. The
> problem is when
> the serial goes down. If IP activates the ISDN, the DECNET
> routes enter the
> routing table. However, when the BRI closes the routes age out of the
> routing table.
>
> R1---------Serial-------------R2
> \ /
> \ /
> \ /
> \------ISDN-------/
>
>
> My solution was a DECNET default route. However, if I use the distant
> DECNET address as the destination, the routing fails because
> the recursive
> lookup for the distance route has aged out. If I use the
> interface as the
> destination, the encapsulation fails because the dialer map
> uses the distant
> address.
>
> Anyone have a solution?
>
> Thanks,
> Matt Holbert
> Network Engineer
> Integrated Communication Solutions, Inc.
> mholbert@icscorp.com
> http://www.icscorp.com
>
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