Unicasting eigrp messages using nat -do not get it

From: nenad pudar (nenad.pudar@gmail.com)
Date: Mon Jan 02 2006 - 00:47:38 GMT-3


Hi guys

I am trying to unicast the eigrp update between two neighbors using nat
It is working but I do not understand the principe behind this

Here is the config
interface Virtual-Template1
 bandwidth 512
 ip address 172.16.32.130 255.255.255.192
 ip nat outside **************************************
 ip authentication mode eigrp 2 md5
 ip authentication key-chain eigrp 2 ccie
 ip summary-address eigrp 2 10.17.2.0 255.255.255.0 5
 ppp authentication chap PPP
 ppp chap hostname r1
end

ip nat outside source static 172.16.32.129 224.0.0.10 ********************

#R1sh ip eigrp neighbors
IP-EIGRP neighbors for process 2
H Address Interface Hold Uptime SRTT RTO Q Seq
Type
                                            (sec) (ms) Cnt Num
0 172.16.32.129 Vi1 14 00:00:18 1 5000 1 0

IP-EIGRP neighbors for process 3

.855: NAT: s=172.16.32.130, d=224.0.0.10->172.16.32.129 [0]
Jan 2 03:23:46.199: NAT: i: eigrp (172.16.32.130, 0) -> (224.0.0.10, 0) [0]
Jan 2 03:23:46.199: NAT: s=172.16.32.130, d=224.0.0.10->172.16.32.129 [0]
Jan 2 03:23:50.783: NAT: i: eigrp (172.16.32.130, 0) -> (224.0.0.10, 0) [0]
Jan 2 03:23:50.783: NAT: s=172.16.32.130, d=224.0.0.10->172.16.32.129 [0]
Jan 2 03:23:55.535: NAT: i: eigrp (172.16.32.130, 0) -> (224.0.0.10, 0) [0]
Jan 2 03:23:55.535: NAT: s=172.16.32.130, d=224.0.0.10->172.16.32.129 [0]
Jan 2 03:24:00.271: NAT: i: eigrp (172.16.32.130, 0) -> (224.0.0.10, 0) [0]
Jan 2 03:24:00.271: NAT: s=172.16.32.130, d=224.0.0.10->172.16.32.129 [0]

#R1sh ip nat translations
Pro Inside global Inside local Outside local
Outside global
--- 172.16.32.130 172.16.32.130 224.0.0.10
172.16.32.129

I did this following one similar example in Cisco book but I do not get it

ip nat outside source static 172.16.32.129 224.0.0.10 statement according to
my understanding of how NAT works will:

1) Translate the source address 172.16.32.129 to 224.0.0.10 once the packet
hits outside interface
2) It will also translate the destination address 224.0.0.10 to
172.16.32.129 once the packet hits the inside interface

Above you can see the nat log

This statement

Jan 2 03:23:46.199: NAT: s=172.16.32.130, d=224.0.0.10->172.16.32.129

I can understand assuming that since the packet are locally generated router
"does not need explicitly defined inside interface"

But I do not really get what is happening with the packet coming from the
other side

 Anybody can help me about this one .

thanks
nenad



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