We have a straight forward internet connection which has a small /29 IP range. The connection is Ethernet and our default gateway is the first IP in the /29 range.
Our ISP has just given us a secondary IP range, a /28. They have told us that we need to use the first IP of that range as our default gateway.
Now the device it's connected to is a Juniper SRX.
Initially I thought this wouldn't be an issue but it turns out it's more tricky than I thought.
- I can't just use any of the new IP addresses on the existing untrust interface because traffic isn't routed back to the correct gateway.
- I can use a virtual router as the networks both come in over the same Ethernet cable and are plugged into a single interface
I was thinking that maybe I need to use source or policy based routing.
Does anyone have any ideas? Should I go back to them and ask for them to just route the new /28 subnet to IP address of the SRX in the original /29? Is PBR/SBR the way to go?
The only thing I know about their config is that the device is a Cisco and has the following config snippet
interface FastEthernet1/0/2 description *** Link into customer LAN *** no switchport ip address 220.127.116.11 255.255.255.240 secondary ip address 18.104.22.168 255.255.255.248 #ping 22.214.171.124 source 126.96.36.199 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 188.8.131.52, timeout is 2 seconds: Packet sent with a source address of 184.108.40.206 !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 16/20/26 ms