Code:
xxxxx@USG:~$ show ip route 192.168.100.0
Routing entry for 0.0.0.0/0
Known via "static", distance 1, metric 0, best
* directly connected, pppoe0
xxxxx@USG:~$ traceroute 192.168.100.1
traceroute to 192.168.100.1 (192.168.100.1), 30 hops max, 38 byte packets
1 * * *
2 * * *
3 31.55.187.180 (31.55.187.180) 3.616 ms 4.729 ms 31.55.187.176 (31.55.187.176) 3.639 ms
4 * * *
5 * * *
6 * * *
7 *^C
xxxxx@USG:~$
Fortigate too, this is a 200E. I've heavily reacted it to keep my employers name out of it:
Code:
xxxxxxxxxx-200E-01 # get router info routing-table all | grep 192.168.100.0
xxxxxxxxxx-200E-01 # exec traceroute 192.168.100.1
traceroute to 192.168.100.1 (192.168.100.1), 32 hops max, 3 probe packets per hop, 84 byte packets
1 xxx.xxx.xxx.xxx <ptr removed> 2.989 ms 2.946 ms 2.895 ms
2 xxx.xxx.xx.xx <ptr removed> 3.009 ms 2.951 ms 2.908 ms
3 * * *
4 * * *
5 * * *
6 * *^C *
So as expected none of the traces completed but both devices did try and route to it even though the destination was an RFC1918 address. They simply followed the default route.
IOS and Meraki (as much as I dislike Meraki) don't care either though I haven't got access to anything right now to grab some data.
I know at least some Netgear, TP-Link, Linksys & Belkin (sorry for swearing) stuff does too. I was last a Virgin Media customer about 8 years ago and used all sorts of different consumer grade routers. All of which allowed me to access the management interface of the SuperHub on 192.168.100.1 without needing any configuration.
I've also spoken to a colleague recently who was trying to access some work stuff by IP address (all RFC1918) but failing. When he sent me a trace it turns out he hadn't connected to the VPN but his Fritz Box was chucking the traffic out of the WAN port.
Edit - The TACACS server decided to play nicely so I grabbed some (reacted) data from a Cisco 927. Looking through the config there's nothing special about how it deals with RFC1918 destinations, here's it's just following the BGP learnt default route:
Code:
xxxxx-xx-xxxx-xxx-xxxxx#sh ip ro 192.168.100.0
% Network not in table
xxxxx-xx-xxxx-xxx-xxxxx#traceroute 192.168.100.1
Type escape sequence to abort.
Tracing the route to 192.168.100.1
VRF info: (vrf in name/id, vrf out name/id)
1 xx.xx.xx.xxx 0 msec 0 msec 0 msec
2 xx.xx.xx.xxx [AS xxxx] 0 msec 4 msec 4 msec
3 xx.xx.xx.xx [AS xxxx] 12 msec 8 msec 8 msec
4 xx.xx.xx.xx [AS xxxx] 16 msec 12 msec 12 msec
5 * * *
6 * * *
7 * * *
8 * * *
9 * * *
10 * * *
Edit 2 - I got a colleague using whatever the current TalkTalk CPE is to try:
Code:
Tracing route to 192.168.100.1 over a maximum of 30 hops
1 1 ms <1 ms <1 ms ttrouter [10.0.10.1]
2 5 ms 5 ms 5 ms ae51-ner001.mlk.as13285.net [78.144.1.25]
That doesn't care either and sends it down the default route.