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EdgeRouter Lite: no WAN access due to ISP's DHCP returning /32 for WAN IP and default router

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Hi,

I'm struggling to setup my EdgeRouter Lite that won't allow me internet access due to /32 IP and default router addresses.

Here's the situation:
My ISP delivers (through DHCP) the following to the ERL:
- its WAN IP as /32, say 1.2.3.4/32
- its default router, again as /32, say 5.6.7.8/32
- various info such as DNS servers etc.

Using the Basic setup wizard configuration, the ERL is not able to route through the default router. My analysis is that eth0 has no IP address belonging to the IP network of the default router. I checked this using static addresses (and fake netmasks) instead of DHCP.
This is due to the router WAN IP and default router being defined as /32. More, the WAN IP AND the default router obviously DON'T belong to the same net as in example IPs above.
Strangely, the default router is reachable, I can ping it and get its MAC address.
Some other routers have no issue with this configuration, and my Mac directly connected without the ERL is happy with it too.

I'm pretty sure the ERL is able to handle this. I just don't know how to achieve this, so I'm asking for your help.

Thanks in advance,

Pascal;


Here are a few info gathered from the ERL, IP have been changed to match above example:

GUI routes:
Selected  Destination  Next Hop  Interface  Route Type
Yes       0.0.0.0/0    5.6.7.8              Static
Yes       127.0.0.0/8            lo         connected
Yes       5.6.7.8/32             eth0       Static
Yes       1.2.3.4/32             eth0       connected
Yes       192.168.1.0/24         br0        connected
(The above looks correct to me)

 

ubnt@ubnt:~$ show ip route
Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
> - selected route, * - FIB route, p - stale info
IP Route Table for VRF "default"
S    *> 0.0.0.0/0 [210/0] via 5.6.7.8 (recursive is directly connected, eth0) )
C    *> 127.0.0.0/8 is directly connected, lo
S    *> 5.6.7.8/32 [210/0] is directly connected, eth0
C    *> 1.2.3.4/32 is directly connected, eth0
C    *> 192.168.1.0/24 is directly connected, br0
(The above looks correct to me, ERL even detects the "directly connected" situation)

 

ubnt@ubnt:~$ netstat -rn
Kernel IP routing table
Destination  Gateway  Genmask         Flags MSS Window irtt Iface
0.0.0.0      0.0.0.0  0.0.0.0          U      0 0         0 eth0
5.6.7.8      0.0.0.0  255.255.255.255  UH     0 0         0 eth0
1.2.3.4      0.0.0.0  255.255.255.255  UH     0 0         0 eth0
192.168.1.0  0.0.0.0  255.255.255.0    U      0 0         0 br0
(
Here, the first line looks wrong to me, I expected the Gateway for 0.0.0.0 to be 5.6.7.8)

 

The default router is reachable. I can ping it and get its MAC address from ERL shell:
ubnt@ubnt:~$ sudo ping -n 5.6.7.8
(default router replies)
ubnt@ubnt:~$ sudo arp -an
? (5.6.7.8) at 74:8e:f8:xx:xx:xx [ether] on eth0

 

FWIW: 1 Gb/s symetric fiber connection

 


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