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static route basic - directly connected interface

SJ K
Level 5
Level 5

Dear all,

 

I have 3 routers connected to one another

 

R1 <-> R2 <-> R10

R1 fa0/0 (192.168.3.1)  -- R2 fa0/0 (192.168.3.2)  (192.168.3.0/24 network)
R2 fa0/1 (192.168.5.1) - R10 fa0/0 (192.168.5.2)   (192.168.5.0/30 network)
I do not have gateway of last resort set across all the routers.

on R1, i created a static route
ip route 192.168.5.0 255.255.255.252 fa0/0

on R3, i created a static route
ip route 192.168.3.0 255.255.255.0 fa0/0


R1#ping 192.168.5.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.5.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 108/128/168 ms

Voila, success.

 

Q1) But i am starting to think of when R1 is creating the packet to be send out, how does R1 know what to input for the [DST MAC] address ?

e.g. R1 packet -> [Src IP = 192.168.3.1] [Dst IP = 192.168.5.2] [Src mac = R1faf0/0 mac] [Dst mac = ???]

I do not have any default gateway set on R1 and on my static route to 192.168.5.0/30 network, I have only specify the exit interface which is R1 fa0/0.


How does R1 know to specify the R2 Fa0/0 as the mac address for the [Dst Mac] portion ?

 

Q2) How does R1 know of R2 mac address ?  Is it that for directly connected interface, the interface on the other end (e.g R2 Fa0/0) is automatically set as the destination gateway for that particular network and its mac address automatically discover ?

 

Regards,

Noob

15 Replies 15

Dear Jon, Richard and all,

Thanks for reverting.

Yeap, clearing the arp cache and doing the wireshark capture shows that R1 is sending out the arp request and R2 is responding to it with its own MAC.

Disabling proxy-arp on R2 and my ping failed. Yeah!

 

At the same time, i finally get some answer on why my lecturer in the past ask us to use the next hop address instead of the direct connected interface ;)

 

Thanks all! Its cool to get the concepts working on the practical ;)

 

Regards,
Noob

 

Regards,

Noob