Take the 2-minute tour ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Like if host address is 100.0.0.1 and next hop address is 100.0.0.2 and destination ip address is also 100.0.0.2

Is this a valid use case? Any real life usage?

          <dest ip>                 <next hop>  
ip route 100.0.0.2 255.255.255.255 100.0.0.2 weight 1 next-hop-vrf GlobalRouter

Above is the command on a router inside a VRF. 100.0.0.2 is pingable from host. 100.0.0.1 & 100.0.0.2 are an ip address assigned to a VLAN on host & destination respectively.

On a linux box, Such configuration is valid.

[root]# netstat -r -n

Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
55.55.55.55     55.55.55.55     255.255.255.255 UGH       0 0          0 eth0

[root]# ip route show

55.55.55.55 via 55.55.55.55 dev eth0

As per my understanding, If a destination IP is reachable (i.e in the same subnet of host IP) we dont need a next hop.

I came across one application for using next hop for destination IP in same subnet (i.e for VPN) See this: Will packets send to the same subnet go through routers?

If next hop != destination IP but they are in same subnet as that of host, is a valid scenario for VPN, then i am wondering what are the applications of next_hop==dest_ip & subnet same as host?

This is my first post in Super User. Extremely happy with the quick and warm response.

share|improve this question

closed as off-topic by Dave, Ƭᴇcʜιᴇ007, Nifle, Tog, m4573r May 29 at 10:03

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question is not about computer hardware or software, within the scope defined in the help center." – Dave, Ƭᴇcʜιᴇ007, Tog, m4573r
If this question can be reworded to fit the rules in the help center, please edit the question.

    
How on earth has this got 4 close votes? –  barlop May 28 at 12:43
    
I notice in my routing table, win7 on a comp with IP of 10.0.0.2 there is a line that says- 10.0.0.2 255.255.255.255 On-link 10.0.0.2 276 I am a bit rusty though. –  barlop May 28 at 12:44
    
Somebody asked about ARP and that was considered OK. Why not this question? –  barlop May 28 at 12:45
    
raj, in that last line, is that meant to be a command or is that meant to be output? i either way, better to provide a screenshot so we can see OS and column headings and what it looks like really –  barlop May 28 at 14:32
    
Thanks barlop for the response. Updated the question –  Raj May 28 at 17:57

1 Answer 1

I don't know what ip command you're using, but the next hop can of course be the destination. This is what always happens at the last hop.

If you want a closer example, you can often configure your router by going to its IP (like 192.168.1.1). In this case the next hop is the destination and there is only a single hop.

share|improve this answer
    
I think what he is getting at, is that philosophically, when you're at the destination, there is no 'next hop' because it's not hopping on to another router. But, in networking, if there is a next hop at the destination that lists itself, then Why? I suppose perhaps the answer is that there it is listed as next hop and does indicate it reached the destination. But philosophically it could have sone code that just says Accept and don't route. That is essentially what it is doing. –  barlop May 28 at 12:47
    
The next hop is not at the destination itself. The device which has a next hop in his question is 100.0.0.1, which has a route to 100.0.0.2 telling it to send the packet directly to 100.0.0.2, because 100.0.0.2 is on the same link so reachable in a single hop. –  user2313067 May 28 at 12:50
    
At the end of his question he gives another example - the example of "ip route 100.0.0.3 255.255.255.255 100.0.0.3" So in that example he gave there, the next hop is to the same device(computery "router) that the packet just came "in" on. That packet is not going to go anywhere else other than that device. So the destination is the next hop, in that example. –  barlop May 28 at 13:02
    
When I try his command, it gives me Command "100.0.0.3" is unknown, try "ip route help"., so I don't really know what his command means. I took it to mean route 100.0.0.3/32 via 100.0.0.3 (so on-link). Since the computer/router the command is run on is 100.0.0.1 as far as I understand, the destination is not the sender itself but another machine on the same link, I do not see a problem. –  user2313067 May 28 at 13:22
    
well what would you make of this output i.imgur.com/8jyVf2n.png That is done on a computer with IP 10.0.0.2 and an entry in its routing table has IP 10.0.0.2 in the far left part("incoming"? part), and 10.0.0.2 on the on the far right (next hop part?) (dest=next hop=device its on) –  barlop May 28 at 13:47

Not the answer you're looking for? Browse other questions tagged or ask your own question.