Routing table remote routes question.

[khabkean]

I got this answer wrong in an essay question.

Question - " In a routing table, why does a remote route have a ip address " We were to assume this was an ethernet network.

My answer - The IP in the routing table is used for arp, so the packet can be encapsulated in a 802.3 ethernet frame. IP is required for arp to find the mac address of the remote routers nic so the frame can be delivered to that router for further routing.

Am I miss understanding something? Is that process wrong?

[Kasun Bandara]

ip routing table using to routing purpose. you have 2 main types of routes. 

1. locally connected routes

2. remote network routes

for locally connected networks, router will automatically create connected routes which are having AD 0.

for remote networks, routers need some destination IP address (another routing capable device) to send remote network destined traffic.

[Jon Marshall]

I assume they are talking about the next hop IP in the question. 

You haven't musunderstood the process so it's difficult to see why the answer is wrong, the only thing I can think of is your wording ie. the IP is not required for arp, the IP is required so the router knows where to forward the packets and it uses arp to then resolve the IP address to the mac address of the next hop. 

Often the question is looking for a specific answer but your understanding of how it works seems fine to me which is more important. 

Jon

[Kasun Bandara]

right, as i understood the Q, its asking about next hop IP. so we dont need to discuss about ARP here. next hop IP is required to router for populate ip routing table for remote network

[MHM Cisco World]

https://www.cisco.com/c/en/us/support/docs/dial-access/floating-static-route/118263-technote-nexthop-00.html

see doc. this answer your question 

static route can config with outlet interface 
except the ethernet 
need next-hop and outlet interface.

[Richard Burts]

I find the essay question in the original post a bit ambiguous. Generally a route entry in a routing table has 2 IP addresses. It has an address that identifies the remote destination and it has an address for the next hop (the exception to this is a static route which identifies an outbound interface but not a next hop). So which address is the question asking about? The answers are quite different, depending on which one it is asking about.

There is a basis for saying that your answer was not correct, no matter which address the question was about. You say "My answer - The IP in the routing table is used for arp". But the question specifies that this is a remote route. You arp when the destination is in the local subnet and for remote destinations you just forward to your default gateway.

[Jon Marshall]

But you arp for your default gateway as well. 

It can be read a number of ways but the fact it referred to an IP address rather than a network or subnet suggested to me it was the next hop IP they were referring to. 

Jon

[Richard Burts]

Jon

I don't want to be overly picky, but his response did not say ping for the gateway address. It said "The IP in the routing table is used for arp".

We both agree that the essay question was poorly worded and is ambiguous. It is a reasonable interpretation that it was referring to the next hop address. But it is also a reasonable interpretation that it was referring to the destination  address (might be host, might be subnet, might be network depending on masking). 

[Jon Marshall]

Rick

Agreed, it could be read either way, just seemed to me that the OP did understand the actual process even if he worded it incorrectly for the question. 

But yes, if it was referring to the subnet it would be incorrect. 

Seems the main issue is with the wording of the question really. 

Jon

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[Richard Burts]

Jon

We absolutely agree that the main issue is poor wording of the essay question.

And I can agree that if you assume the question refers to the next hop address that his explanation did describe that process fairly well.