Mobile ARP

Well seeing as how I just missed a 4-point task on mobile ARP, I thought now was a good time to learn it. It's actually very simple and pretty cool once you get it working.

Topology is a little confusing so here it is in 2 parts:

PHYSICAL:

R1---CAT1===dot1q===CAT2---R8

LOGICAL:

VLAN 100---R1---R2---R5---R7---R8---VLAN 200

The task says that users on R8's LAN occasionally mover over to R1's LAN. They still need access to the network. What we do is configure R1 to listen for ARP packets from R8's subnet (VLAN 200).

We can test this by creating an SVI for VLAN 100 and giving it an IP in R8's subnet. When it tries to contact anyone, we will see a mobile route appear in R1's route table. This route then gets redistributed into the routing protocol (OSPF in this case). It appears as a /32 route so the longer match wins over any other route advertisement of VLAN 200.

All configuration is on R1:

1) CREATE THE ACL

R1(config)#access-list 8 permit 172.31.80.0 0.0.0.255


2) CONFIGURE MOBILE ARP ON INTERFACE

R1(config)#interface f0/0
R1(config-if)# ip mobile arp access-group 8


3) REDISTRIBUTE

R1(config)#router ospf 1
R1(config-router)# redistribute mobile subnets


4) VERIFY

Ceate an SVI on VLAN 100 with VLAN 200 IP address:

CAT1(config)#int vlan 100
CAT1(config-if)#ip address 172.31.80.100 255.255.255.0
CAT1(config-if)#^Z
CAT1#ping 172.31.80.8

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.31.80.8, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/219/1016 ms

Run debug and show commands on R1:

R1#debug ip mobile
IP mobility events debugging is on
Nov 29 21:17:14.138: Local MobileIP: route add 172.31.80.100

R1#show ip route mobile
172.31.0.0/16 is variably subnetted, 11 subnets, 6 masks
M 172.31.80.100/32 [3/1] via 172.31.80.100, 00:11:05, FastEthernet0/1
R1#

Traceroute shows how many hops we are actually going through:

CAT1#trace 172.31.80.8

Type escape sequence to abort.
Tracing the route to 172.31.80.8

1 172.31.10.1 4 msec 4 msec 0 msec
2 172.31.12.2 0 msec 4 msec 0 msec
3 172.31.100.5 12 msec 8 msec 12 msec
4 172.31.200.7 12 msec 8 msec 12 msec
5 172.31.78.8 12 msec * 8 msec
CAT1#

IPexpert Volume 2 Section 12 Review

I woke up late for this one but I still finished in plenty of time. Probably about 4 hours. I made some serious mistakes though that I completely overlooked. It was in the BGP section, I didn't configure a confederation...so that may have ruined 2 or 3 tasks - not real sure how to gauge the impact. You should have seen the look on my face when I saw the PG.

With that included I missed 6 tasks for about 15 points:

-8 Tasks 8.1 - 8.3
I knew we were using private AS numbers so I immediately thought configuring a confederation. However, I did not deduce that from the task requirements so I didn't bother. Reviewing it, I completely overlooked R1's task of peering with R2 is AS 200. AS 200 should have been the confederation....BIG BOOBOO. Completely unacceptable.

-4 Task 9.3 IOS Services
Completely missed this "Mobile ARP" section. I had a NAT solution that does what I thought the task asks. I have no idea how to configure mobile arp and I guess it's time to learn. I wonder if anyone even uses it...

-2 Task 11.2 DHCP
I used "no ip bootp server" for the DHCP router not respond to bootp requests. However, the answer was "ip dhcp bootp ignore"

-1 Task 14.3 Multicast
Configured MRM incorrectly. I used the DocCD for this and was what you could call "way off." It was a 1 point task and I was not too concerned.

My goal from here on out is to keep my score above 80 while improving my "process." That includes verifying everything, making notes and a point tracker, refraining from marking the actual lab docs (which I heard you cannot do), and moving through the DocCD.

Missing the BGP confederation is something that should never happen. I am lucky there were not more tasks dependent on it. Everything else was filtering of some sort. Who knows, I may have been marked of on the entire BGP section (20 points).

One thing I worry about is that I have not really been challenged during Layer 2 configurations. I pretty much breeze through VTP, trunking, and other topics, but I know there are topics that will get me (QoS, tunneling). For these I rely on the DocCD and make my own labs. That being said, Volume 1 Section 5 has an extremely difficult tunneling lab that I need to review.

BGP - Conditional route injection

Topology

R5----R7

R5 is advertising 10.34.19.0/26 to R7
Configure R7 to inject 10.34.19.48/28

1) MAKE PREFIX-LISTS

ip prefix-list EXIST seq 5 permit 10.34.19.0/26
ip prefix-list INJECT 5 permit 10.34.19.48/28
ip prefix-list SOURCE seq 5 permit 192.168.5.5/32


2) MAKE ROUTE-MAPS

route-map INJECT permit 10
set ip address prefix-list INJECT

route-map EXIST permit 10
match ip address prefix-list EXIST
match ip route-source prefix-list SOURCE


3) CONFIGURE BGP

route bgp 567
bgp inject-map INJECT exist-map EXIST


4) VERIFY

R5#show ip bgp nei 192.168.7.7 advertised-routes | begin Net
Network Next Hop Metric LocPrf Weight Path
*> 10.34.19.0/26 192.168.2.2 0 200 0 24 1 i

R7#show ip bgp injected-paths | begin Net
Network Next Hop Metric LocPrf Weight Path
*>i10.34.19.48/28 192.168.5.5 0 200 0 24 1 i

Things to remember:

- Must use Prefix-lists, NOT ACLs
- Injected route must a subset of am aggregate already in the table
- Use "set" command for inject-map, not "match"
- I commonly forget the "prefix-list" argument when configuring the maps
- inject-map Command is a bgp command, not per-neighbor