Observe the following network presented in this exhibit carefully. Assume that all routers are running EIGRP in AS 100 on all connected links. If the link between PG-R3 and PG-R4 is down, how many queries will PG-R5 and PG-R6 receive?
A.
PG-R6 will receive two queries, one for 192.168.1.0/24 and one for 192.168.2.0/24. PG-R5 will receive one query, for 192.168.1.0/24.
B.
PG-R5 will receive one query, for 192.168.1.0/24, and PG-R6 will receive no queries
C.
Both PG-R5 and PG-R6 will receive two queries, one for 192.168.1.0/24 and one for 192.168.2.0/24
D.
Neither PG-R5 nor PG-R6 will receive any queries for either 192.168.1.0/24 or 192.168.2.0/24.
Explanation:
Some sources select choice A but I don’t think distribution list is applicable when a query is being sent hence my choice of C
The answer is A. This is because the query for 192.168.1.0/24 will not be propagated from r5 to r6. EIGRP routers do not propagte queries for routes they do not know about. The distribution list stops r5 from learning 192.168.1.0/24 so r5 will not forward the query. Note the distribution list does not block the query from r4 to r5 so you are correct that the distribution list does not block queries but the effect of the distribution list does. Google for eigrp query scoping.
Hi everyone,
I made the exact GNS3 version of the question as seen above with most basic config.But the result is neither of them above.R5 receives one query for 192.168.1.0/24 and one query for 192.168.2.0/24 and R6 receives just one query for 192.168.1.0/24. R6 doesnt even know if 192.168.2.0/24 network was exist.
Addressing scheme and R5’s and R6’s (debug eigrp packets query and debug eigrp fsm) outputs are listed below.
Ip Addressing / R1-R3 : 10.0.0.0/30
R2-R3 : 10.0.0.4/30
R3-R4 : 10.0.0.8/30
R4-R5 : 10.0.0.12/30
R5-R6 : 10.0.0.16/30
R1’s Loopback 1 : 192.168.1.1/24
R2’s Loopback 2 : 192.168.2.1/24
After shutting down R4’s interface that connects to R3 ;
R5’s debug output is ;
R5#
*Mar 1 00:22:34.759: EIGRP: Received QUERY on FastEthernet0/0 nbr 10.0.0.13
*Mar 1 00:22:34.759: AS 100, Flags 0x0, Seq 52/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
*Mar 1 00:22:34.763: DUAL: dest(10.0.0.8/30) not active
*Mar 1 00:22:34.763: DUAL: rcvquery: 10.0.0.8/30 via 10.0.0.13 metric 4294967295/4294967295, RD is 4294967295
*Mar 1 00:22:34.763: DUAL: send REPLY(r1/n1) about 10.0.0.8/30 to 10.0.0.13
*Mar 1 00:22:34.767: DUAL: dest(10.0.0.0/30) not active
*Mar 1 00:22:34.767: DUAL: rcvquery: 10.0.0.0/30 via 10.0.0.13 metric 4294967295/4294967295, RD is 4294967295
*Mar 1 00:22:34.767: DUAL: send REPLY(r1/n1) about 10.0.0.0/30 to 10.0.0.13
*Mar 1 00:22:34.767: DUAL: dest(10.0.0.4/30) not active
*Mar 1 00:22:34.767: DUAL: rcvquery: 10.0.0.4/30 via 10.0.0.13 metric 4294967295/4294967295, RD is 4294967295
*Mar 1 00:22:34.771: DUAL: send REPLY(r1/n1) about 10.0.0.4/30 to 10.0.0.13
*Mar 1 00:22:34.771: DUAL: rcvquery: 192.168.1.0/24 via 10.0.0.13 metric 4294967295/4294967295, RD is 161280
*Mar 1 00:22:34.771: DUAL: Find FS for dest 192.168.1.0/24. FD is 161280, RD is 161280
*Mar 1 00:22:34.771: DUAL: 10.0.0.13 metric 4294967295/4294967295 not found Dmin is 4294967295
*Mar 1 00:22:34.771: DUAL: Peer total/stub 2/0 template/full-stub 2/0
*Mar 1 00:22:34.771: DUAL: Dest 192.168.1.0/24 entering active state.
*Mar 1 00:22:34.771: DUAL: Set reply-status table. Count is 1.
*Mar 1 00:22:34.771: DUAL: Doing split horizon on FastEthernet0/0
*Mar 1 00:22:34.771: DUAL: Going from state 1 to state 3
*Mar 1 00:22:34.771: DUAL: dest(192.168.2.0/24) not active
*Mar 1 00:22:34.771: DUAL: rcvquery: 192.168.2.0/24 via 10.0.0.13 metric 4294967295/4294967295, RD is 4294967295
*Mar 1 00:22:34.771: DUAL: send REPLY(r1/n1) about 192.168.2.0/24 to 10.0.0.13
*Mar 1 00:22:34.783: EIGRP: Enqueueing QUERY on FastEthernet1/0 iidbQ un/rely 0/1 serno 46-47
*Mar 1 00:22:34.787: EIGRP: Sending QUERY on FastEthernet1/0
*Mar 1 00:22:34.787: AS 100, Flags 0x0, Seq 42/0 idbQ 0/0 iidbQ un/rely 0/0 serno 46-47
*Mar 1 00:22:34.827: DUAL: Removing dest 10.0.0.8/30, nexthop 10.0.0.13
*Mar 1 00:22:34.827: DUAL: No routes. Flushing dest 10.0.0.8/30
*Mar 1 00:22:34.831: DUAL: Removing dest 10.0.0.0/30, nexthop 10.0.0.13
*Mar 1 00:22:34.831: DUAL: No routes. Flushing dest 10.0.0.0/30
*Mar 1 00:22:34.831: DUAL: Removing dest 10.0.0.4/30, nexthop 10.0.0.13
*Mar 1 00:22:34.831: DUAL: No routes. Flushing dest 10.0.0.4/30
*Mar 1 00:22:34.831: EIGRP: Enqueueing QUERY on FastEthernet0/0 iidbQ un/rely 0/1 serno 46-46
*Mar 1 00:22:34.835: DUAL: dest(192.168.1.0/24) active
*Mar 1 00:22:34.835: DUAL: rcvreply: 192.168.1.0/24 via 10.0.0.18 metric 4294967295/4294967295
*Mar 1 00:22:34.839: DUAL: reply count is 1
*Mar 1 00:22:34.839: DUAL: Clearing handle 1, count now 0
*Mar 1 00:22:34.839: DUAL: Freeing reply status table
*Mar 1 00:22:34.839: DUAL: Find FS for dest 192.168.1.0/24. FD is 4294967295, RD is 4294967295 found
*Mar 1 00:22:34.839: DUAL: send REPLY(r1/n1) about 192.168.1.0/24 to 10.0.0.13
*Mar 1 00:22:34.843: DUAL: Removing dest 192.168.1.0/24, nexthop 10.0.0.18
*Mar 1 00:22:34.843: DUAL: Going from state 3 to state 1
*Mar 1 00:22:34.843: EIGRP: Sending QUERY on FastEthernet0/0
*Mar 1 00:22:34.843: AS 100, Flags 0x0, Seq 43/0 idbQ 0/0 iidbQ un/rely 0/0 serno 46-46
*Mar 1 00:22:34.903: DUAL: Removing dest 192.168.2.0/24, nexthop 10.0.0.13
*Mar 1 00:22:34.903: DUAL: No routes. Flushing dest 192.168.2.0/24
*Mar 1 00:22:34.903: DUAL: Removing dest 192.168.1.0/24, nexthop 10.0.0.13
*Mar 1 00:22:34.907: DUAL: No routes. Flushing dest 192.168.1.0/24
R5#
And R6’s debug output is ;
R6#
*Mar 1 00:22:29.855: EIGRP: Received QUERY on FastEthernet0/0 nbr 10.0.0.17
*Mar 1 00:22:29.855: AS 100, Flags 0x0, Seq 42/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
*Mar 1 00:22:29.859: DUAL: rcvquery: 192.168.1.0/24 via 10.0.0.17 metric 4294967295/4294967295, RD is 163840
*Mar 1 00:22:29.859: DUAL: Find FS for dest 192.168.1.0/24. FD is 163840, RD is 163840
*Mar 1 00:22:29.859: DUAL: 10.0.0.17 metric 4294967295/4294967295 not found Dmin is 4294967295
*Mar 1 00:22:29.859: DUAL: Peer total/stub 1/0 template/full-stub 1/0
*Mar 1 00:22:29.859: DUAL: Dest 192.168.1.0/24 (Split Horizon) not entering active state.
R6#
*Mar 1 00:22:29.859: DUAL: send REPLY(r1/n1) about 192.168.1.0/24 to 10.0.0.17
*Mar 1 00:22:29.931: DUAL: Removing dest 192.168.1.0/24, nexthop 10.0.0.17
*Mar 1 00:22:29.931: DUAL: No routes. Flushing dest 192.168.1.0/24
R6#
If i’ve made anything wrong , please let me know.Thank you.
Best Regards , Ferzan Unlu
Chris’s answer is wrong. A distribute list does not stop a query:
http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094cb7.shtml#distlistsaffect
and I think he’s confused on which network he’s talking about.
I believe answer A “should” say:
R5 will receive two queries, one for 192.168.1.0/24 and one for 192.168.2.0/24. R6 will receive one query, for 192.168.1.0/24
What you see is what I would expect. For 192.168.2.0/24, R5 doesn’t know of that network so it will immediately reply unreachable. R5 will also get queried for 192.168.1.0/24. Since this query is from its successor and it has no FS, it will mark the route unreachable, go active on it and query all its neighbors except for the neighbor it received the query from.
R6 will get this query from R5 for 192.168.1.0/24. So R6 only gets 1 query.
Check out this link:
http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094cb7.shtml#queryrange
Yes Robert , You’re right. We got same results.
Generally speaking I agree with Robert’s explanation.
But I have another choice for you. Namely “D”.
Why?
To start EIGRP on all R4 interfaces one should type “network 0.0.0.0 255.255.255.255”. The command “network 0.0.0.0 0.0.0.0” does not start EIGRP on any interface hence – no EIGRP – no queries. 😀