CCIE Pursuit Blog

April 25, 2008

Question Of The Day: 25 April, 2008

Topic: EIGRP

r1 and r2 are directly connected via their respective fa0/0 interfaces:

r1:
interface FastEthernet0/0
  ip address 10.1.12.1
  ip hold-time eigrp 100 30
  ip hello-interval eigrp 100 5
!
router eigrp 100
  no auto-summary
  network 10.1.12.1 0.0.0.0

r2:
interface FastEthernet0/0
  ip address 10.1.12.2
  ip hold-time eigrp 100 60
  ip hello-interval eigrp 100 10
!
router eigrp 100
  no auto-summary
  network 10.1.12.2 0.0.0.0

Will r1 and r2 for an EIGRP neighbor relationship over the Ethernet link between them?

Click Here For The Answer


Yesterday’s Question

Question Of The Day: 24 April, 2008 

Topic: Route-Maps

The engineer in charge of r1 is tasked with routing packets to r2 (10.1.1.2) if they meet any of the following conditions:

1) Any packets coming in r1’s fa0/0 interface
2) Any packets with the tag 1234
3) Any D EX routes (r1 is only running EIGRP)

The engineer asks you to peer review his solution:

route-map LOOPBACK_AND_VLAN6 permit 10
 match interface FastEthernet0/0
 match tag 1234
 match route-type external
 set ip next-hop 10.1.1.2

Will this route map meet the requirements?

Answer: No.

In a route-map clause with multiple match statements, ALL match statements must be fullfilled. 

Route-Maps for IP Routing Protocol Redistribution Configuration

A match or set command in each clause can be missed or repeated several times, if one of these conditions exist:

If several match commands are present in a clause, all must succeed for a given route in order for that route to match the clause (in other words, the logical AND algorithm is applied for multiple match commands).

In our case only routes with a next-hop out fa0/0 AND a route tag of of 1234 AND a route-type of external will have their next-hop set to 10.1.1.2.  The task requires that ANY of those conditions must be met.

Steve makes a nice catch:

“Is it wrong because the ‘match interface FastEthernet0/0 line will match packets routed _out_ Fa0/0 not in?”

He’s right.  I boned up the first requirement of the question:

match interface (IP)

“To distribute any routes that have their next hop out one of the interfaces specified, use the match interface command in route-map configuration mode.”

We can write the route-map to meet the requirements by putting each requirement in its own separate clause:

route-map LOOPBACK_AND_VLAN6 permit 10
 match interface FastEthernet0/0
 set ip next-hop 10.1.1.2
!
route-map LOOPBACK_AND_VLAN6 permit 20
 match tag 1234
 set ip next-hop 10.1.1.2
!
route-map LOOPBACK_AND_VLAN6 permit 30
 match route-type external
 set ip next-hop 10.1.1.2
!
route-map LOOPBACK_AND_VLAN6 permit 1000

Each clause of the route-map will be evaluated until a match is made.  The last clause is included to override the implicit deny.  That way any packets that do not meet any of the clauses will be routed normally.

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3 Comments »

  1. I am not sure if you prefer people not to answer or if you do not want to spoil it

    Here is my answer for this time anyway

    I do not see any reason why they cannot form a neighbor relationship between them.
    Hold time is included in the Hello Packets of EIGRP

    Comment by Aly — April 25, 2008 @ 10:03 pm | Reply

  2. Doesn’t a Route Map behaves as a Class Map? Could you keep all the match statements in a single Route Map and choose match any?

    The match-all and match-any parameters tell IOS whether to match packets that match all the match commands (match-all) or to match packets that match one or more of the match commands (match-any). If you prefer Boolean logic, match-all means that there is a logical AND between each match command with match-all, and logical OR between each match command with match-any.
    Source: Classification Using Class Maps
    IP Telephony Self-Study Cisco QOS Exam Certification Guide, Second Edition.

    Comment by ASD — April 25, 2008 @ 10:16 pm | Reply

  3. […] Question Of The Day: 25 April, 2008  […]

    Pingback by Question Of The Day: 28 April, 2008 « CCIE Pursuit — April 28, 2008 @ 8:24 am | Reply


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