CCIE Pursuit Blog

April 28, 2008

Internetwork Expert Volume II: Lab 5 – Section 3

Interior Gateway Routing – 20 Points

3.1 OSPF

You need to configure OSPF over the partial-mesh Frame Relay cloud, but you cannot change the OSPF network type on r3:

r2(config-router)#do sh ip os int s0/0/0.1 | i Type
  Process ID 100, Router ID 150.1.2.2, Network Type POINT_TO_POINT, Cost: 64

r3(config-router)#do sh ip os int s0/0:0 | i Type
  Process ID 100, Router ID 150.1.3.3, Network Type NON_BROADCAST, Cost: 65

r4(config-router)#do sh ip os int s0/0 | i Type
  Process ID 100, Router ID 150.1.4.4, Network Type NON_BROADCAST, Cost: 65

r5(config-router)#do sh ip os int s0/0 | i Type
  Process ID 100, Router ID 150.1.5.5, Network Type NON_BROADCAST, Cost: 65

So all that really means is that you’ll need to use the OSPF non-broadcast network type.  You’ll also need to configure neighbor statements.  Since r3 is the only device with direct connections to all of the other routers, you’ll want to make it the DR.

r3(config-router)#do sh ip os nei

Neighbor ID     Pri   State           Dead Time   Address         Interface
150.1.2.2         0   FULL/DROTHER    00:01:46    162.1.0.2       Serial0/0:0
150.1.5.5         0   FULL/DROTHER    00:01:51    162.1.0.5       Serial0/0:0
150.1.4.4         0   FULL/DROTHER    00:01:51    162.1.0.4       Serial0/0:0

The only point that I wasn’t clear on was whether or not to establish a neighbor relationship between r4 and r5.  I did not configure them as peers, but I would have clarified this with the proctor.  If you were to peer these routers then you would need to make one of them the DR so you would need to remove the ‘ip ospf priority 0’ on one of the routers.  You would also need to configure a neighbor statement on the DR.

The IE solution did not peer these routers.

3.2 OSPF

Configure OSPF area 27 on sw1 and then ensure that the only OSPF route it will see is a default route generated by r2.  This sounds like a totally stubby area:

Before:
sw1#sh ip route os
     162.1.0.0/24 is subnetted, 5 subnets
O IA    162.1.55.0 [110/66] via 162.1.27.2, 00:00:15, Vlan27
O IA    162.1.0.0 [110/65] via 162.1.27.2, 00:00:15, Vlan27
O IA    162.1.5.0 [110/66] via 162.1.27.2, 00:00:15, Vlan27
     150.1.0.0/16 is variably subnetted, 5 subnets, 2 masks
O IA    150.1.5.5/32 [110/66] via 162.1.27.2, 00:00:15, Vlan27
O IA    150.1.4.4/32 [110/66] via 162.1.27.2, 00:00:15, Vlan27
O IA    150.1.3.3/32 [110/66] via 162.1.27.2, 00:00:15, Vlan27
O IA    150.1.2.2/32 [110/2] via 162.1.27.2, 00:00:15, Vlan27

After:
r2
(config)#router os 100
r2(config-router)#area 27 stub no-summary

sw1(config)#router os 100
sw1(config-router)#area 27 stub

sw1#sh ip route os
O*IA 0.0.0.0/0 [110/2] via 162.1.27.2, 00:00:41, Vlan27

3.3 EIGRP

“Enable EIGRP on all interfaces of sw2, but do not use redistribution or more than one network statement to accomplish this.”

sw2(config)#ip routi
sw2(config)#router ei 200
sw2(config-router)#net 0.0.0.0

sw2(config-router)#do sh ip ei int
IP-EIGRP interfaces for process 200

                        Xmit Queue   Mean   Pacing Time   Multicast    Pending
Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Vl8                0        0/0         0       0/10           0           0
Vl88               0        0/0         0       0/10           0           0
Fa0/15             1        0/0         1       0/10          50           0
Po32               0        0/0         0       0/10           0           0
Lo0                0        0/0         0       0/10           0           0

3.4 EIGRP

Configure EIGRP to use bandwidth, delay, and load to compute the EIGRP metric.  Bandwidth should be three times more significant than either delay or load.

metric weights (EIGRP)

Command Defaults
tos: 0
k1: 1
k2: 0
k3: 1
k4: 0
k5: 0

You need to be careful with these k-values.  You can use the EIGRP metric equation to decipher which k-value refers to with metric variable:

If k5 equals 0, the composite EIGRP metric is computed according to the following formula:

metric = [k1 * bandwidth + (k2 * bandwidth)/(256 – load) + k3 * delay]

If k5 does not equal zero, an additional operation is performed:

metric = metric * [k5/(reliability + k4)]

k1 = bandwidth
k2 = load
k3 = delay

sw2(config-router)#metric weights 0 3 1 1 0 0

r3(config-router)#do sh ip proto | i EIGRP metric
  EIGRP metric weight K1=3, K2=1, K3=1, K4=0, K5=0

3.5 Default Routing

Configure r3 to adverise a default route to the rest of the OSPF network.

“In order to help prevent traffic black holses ensure that r3 drops traffic for all destinations it does not have a longer match for.”

default-information originate (OSPF)

The software still must have a default route for itself before it generates one, except when you have specified the always keyword.

(Optional) Always advertises the default route regardless of whether the software has a default route.

The IE solution guide has a nice write up about the benifits and pitfalls of the ‘always’ keyword.

3.6 Routing Redundancy

Configure r5 to use the PTP serial interface (no advertised into any IGP) if the Frame Relay connection is lost.  You are allowed to use static routes to accomplish this.

Sounds like a floating static route to me (I wish I would have recognized this on a recent Mock Lab…oh well).

r5(config)#ip route 0.0.0.0 0.0.0.0 162.1.45.4 111

r4(config)#do sh ip route | i via 162.1.0.5
O       162.1.55.0/24 [110/66] via 162.1.0.5, 00:11:12, Serial0/0
O       162.1.5.0/24 [110/66] via 162.1.0.5, 00:11:12, Serial0/0
O       150.1.5.5/32 [110/66] via 162.1.0.5, 00:11:12, Serial0/0

r4(config)#ip route 162.1.55.0 255.255.255.0 162.1.45.5 111
r4(config)#ip route 162.1.5.0 255.255.255.0 162.1.45.5 111
r4(config)#ip route 162.1.5.5 255.255.255.255 162.1.45.5 111

r4(config)#router os 100
r4(config-router)#redist static subnets

Let’s test this by shutting down r5’s connection to the Frame cloud:
r5(config)#int s0/0
r5(config-if)#shut

r5#sh ip route | b Gate
Gateway of last resort is 162.1.45.4 to network 0.0.0.0
 

     162.1.0.0/16 is variably subnetted, 4 subnets, 2 masks
C       162.1.45.4/32 is directly connected, Serial0/1
C       162.1.45.0/24 is directly connected, Serial0/1
C       162.1.55.0/24 is directly connected, FastEthernet0/1
C       162.1.5.0/24 is directly connected, FastEthernet0/0
     150.1.0.0/24 is subnetted, 1 subnets
C       150.1.5.0 is directly connected, Loopback0
S*   0.0.0.0/0 [111/0] via 162.1.45.4 

I did run into a problem with connectivity between r3 and r5:

r3#p 162.1.55.5

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 162.1.55.5, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/9/12 ms

r3#p 162.1.5.5

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 162.1.5.5, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/8/12 ms

r3#p 162.1.45.5

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 162.1.45.5, timeout is 2 seconds:
…..
Success rate is 0 percent (0/5)

r3#p 150.1.5.5

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 150.1.5.5, timeout is 2 seconds:
…..
Success rate is 0 percent (0/5)

r3#sh ip route 162.1.45.5
% Subnet not in table

Makes sense since it’s not being advertised via an IGP (we’ll take care of this during the redistribution task).

r3#sh ip route 150.1.5.5
Routing entry for 150.1.0.0/16
  Known via “eigrp 200”, distance 90, metric 207460, type internal
  Redistributing via eigrp 200
  Last update from 162.1.38.8 on FastEthernet0/0, 00:53:52 ago
  Routing Descriptor Blocks:
  * 162.1.38.8, from 162.1.38.8, 00:53:52 ago, via FastEthernet0/0
      Route metric is 207460, traffic share count is 1
      Total delay is 5100 microseconds, minimum bandwidth is 100000 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 1

Ummmm…..I think I missed a “no auto-summary” somewhere.  🙂

sw2(config-router)#do sh run | b router ei
router eigrp 200
 network 0.0.0.0
 metric weights 0 3 1 1 0 0
 auto-summary

sw2(config-router)#router ei 200
sw2(config-router)#no au

I’ve been doing that a lot lately.  😦

r3#sh ip route 150.1.5.5
% Subnet not in table

That’s odd, I thought that I had a floating static route to the loopback on r4:

r4#sh run | i ip route
ip route 162.1.5.0 255.255.255.0 162.1.45.5 111
ip route 162.1.5.5 255.255.255.255 162.1.45.5 111
ip route 162.1.55.0 255.255.255.0 162.1.45.5 111

Damn these fat fingers!!!!

r4(config)#no ip route 162.1.5.5 255.255.255.255 162.1.45.5 111
r4(config)#ip route 150.1.5.5 255.255.255.255 162.1.45.5 111

r3#sh ip route | i 150.1.5.
O E2    150.1.5.5/32 [110/20] via 162.1.0.4, 00:00:33, Serial0/0:0

r3#p 150.1.5.5

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 150.1.5.5, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/9/12 ms

Much better.

3.7 RIPv2

Easy RIP task.  One slight twist:

“As an additional security precaution configure r1 and r6 so that no unautorized devices can receive RIP updates sent out on VLAN 162.”

neighbor (RIP)

The IE solution guide has r6 advertising VLAN 6 into RIP although it is not mentioned in the task (although it does look like it should be advertised into RIP based on the IGP drawing).

3.8 IGP Redistribution

“Redistribute in the minumum places necessary to gain full reachability thoughout the network.”
“Routers in the OSPF domain should have the miniumum amount of routes neeeded to reach the RIP routes learned from bb3.”
“Do not overlap any address space to accomplish this.”

If you hadn’t figured out that they were asking for a summary route that last requirement kind of makes it obvious.

r4#sh ip route rip
     31.0.0.0/16 is subnetted, 4 subnets
R       31.3.0.0 [120/1] via 204.12.1.254, 00:00:15, FastEthernet0/0
R       31.2.0.0 [120/1] via 204.12.1.254, 00:00:15, FastEthernet0/0
R       31.1.0.0 [120/1] via 204.12.1.254, 00:00:15, FastEthernet0/0
R       31.0.0.0 [120/1] via 204.12.1.254, 00:00:15, FastEthernet0/0
     30.0.0.0/16 is subnetted, 4 subnets
R       30.2.0.0 [120/1] via 204.12.1.254, 00:00:15, FastEthernet0/0
R       30.3.0.0 [120/1] via 204.12.1.254, 00:00:15, FastEthernet0/0
R       30.0.0.0 [120/1] via 204.12.1.254, 00:00:15, FastEthernet0/0
R       30.1.0.0 [120/1] via 204.12.1.254, 00:00:15, FastEthernet0/0

We can try to do this with a single summary but we’ll be overlapping address space, so we need two /14 summaries:

r4(config)#router os 100
r4(config-router)#summary-address 30.0.0.0 255.252.0.0
r4(config-router)#summary-address 31.0.0.0 255.252.0.0

r4#sh ip os sum

OSPF Process 100, Summary-address

30.0.0.0/255.252.0.0 Metric 16777215, Type 0, Tag 0
31.0.0.0/255.252.0.0 Metric 16777215, Type 0, Tag 0

The redistribution task was fairly easy.  There are no mutiple points of mutual redistribution between two protocols.  The only ‘gotcha’ is to remember to advertise the s0/1 interface into OSPF on r4.  This will ensure that we have reachability to 162.1.45.5 if the s0/0 interface goes down on r5 (task 3.6)

With r5’s s0/0 shut down:
r3#p 162.1.45.5

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 162.1.45.5, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/8/12 ms

The IE solution guide has some strangeness on r3:

Task 3.8 on solution guide Why only VLAN162 in

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