Strange routing table entries - cause for concern???

[Chippy_boy]

Fiddling about trying to fix something else, I just happened to notice the following in my RT-N66U routing table:

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
172.16.16.13    *               255.255.255.255 UH    0      0        0 WAN
192.168.1.0     *               255.255.255.0   U     0      0        0 LAN
default         172.16.16.13    0.0.0.0         UG    0      0        0 WAN

Seeing as I have no recollection of setting any of this, and since I have no idea who/where 172.16.16.13 is/are, I am more than a little concerned.

Can anyone offer any reassurance that this is nothing to worry about?

 

[RMerlin]

It's your default route, meaning this is the IP address of your ISP's gateway.

 

[Chippy_boy]

Thanks!

So I can relax then?

Funny how I don't see any such entries in other peoples' routing tables. (Of course I understand every ISP will have a different gateway, but still most tables I have seen look like this:

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.66.1    *               255.255.255.255 UH    0      0        0 WAN
192.168.1.0     *               255.255.255.0   U     0      0        0 LAN
192.168.66.0    *               255.255.255.0   U     0      0        0 WAN
default         192.168.66.1    0.0.0.0         UG    0      0        0 WAN

i.e. everything starts with 192.168.x.x

So why do some routing tables look like this and mine doesn't?

 

[RMerlin]

Thanks!

So I can relax then?

Funny how I don't see any such entries in other peoples' routing tables. (Of course I understand every ISP will have a different gateway, but still most tables I have seen look like this:

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.66.1    *               255.255.255.255 UH    0      0        0 WAN
192.168.1.0     *               255.255.255.0   U     0      0        0 LAN
192.168.66.0    *               255.255.255.0   U     0      0        0 WAN
default         192.168.66.1    0.0.0.0         UG    0      0        0 WAN

i.e. everything starts with 192.168.x.x

So why do some routing tables look like this and mine doesn't?

Do not confuse routes from a computer with routes from a router. In a router's case, there will always need to be a route that points at your ISP's gateway, otherwise the router would be unable to ever reach the Internet. This is also the case on my own router.

The only situation where that wouldn't be the case is if you are double NAT'ed, having your router sit behind another router. This is not an ideal/normal setup however.

 

[Chippy_boy]

Do not confuse routes from a computer with routes from a router. In a router's case, there will always need to be a route that points at your ISP's gateway, otherwise the router would be unable to ever reach the Internet. This is also the case on my own router.

The only situation where that wouldn't be the case is if you are double NAT'ed, having your router sit behind another router. This is not an ideal/normal setup however.

Thanks. This helps me understand a lot.

The thing that now puzzles me is that the routing table above is from an ASUS router, and indeed all of the example routing tables from ASUS routers you find when googling, look like the one above.

Given what you say, I can't imagine they are all sitting in front of other routers. Seems very odd.

Thanks again though.

 

[RMerlin]

Thanks. This helps me understand a lot.

The thing that now puzzles me is that the routing table above is from an ASUS router, and indeed all of the example routing tables from ASUS routers you find when googling, look like the one above.

Given what you say, I can't imagine they are all sitting in front of other routers. Seems very odd.

Thanks again though.

192.168.66.1 is not a public routable IP, so chances are this came from either a setup where the modem was also configured as a router (leading to a double NAT), or this is a CG-NAT-based ISP.