Download EIGRP Troubleshooting

The Active Process
ƒ Where do queries stop?
10.1.1.0/24
ƒ Router A loses its connection
to 10.1.1.0/24
A
B
Router A sends B a query
ƒ Router B examines its local
tables and finds
Local
Knowledge of
an Alternate
Path, so Reply
C
Its current path (successor)
doesn’t pass through A
ƒ Router B answers with a
valid alternative path
E
G
D
ƒ The query is bounded where
there is local knowledge of
another loop-free path
F
H
BRKRST-3330
14494_04_2008_c1
© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Public
41
The Active Process
ƒ Since queries are used to find an alternative path to a
lost destination; where do these queries stop, or do
they just keep circulating through the network?
ƒ One place where a query will stop propagating is where
the router receiving the query has an alternative path
that it can reply with
ƒ In the example above, B receives the query from A,
looks in his topology table and finds that he has a loop
free path to the destination
ƒ B will reply to A with the metric he is using for that
destination so that A can install the path through him to
reach the destination
ƒ There’s no need to send the query on when you have a
good answer yourself
BRKRST-3330
14494_04_2008_c1
© 2008 Cisco Systems, Inc. All rights reserved.
© 2006, Cisco Systems, Inc. All rights reserved.
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Cisco Public
42
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