**Scenario:**
My ISP provides me with multiple DSL connections that have the same IP blocks routed through them which is downstream load balanced by my ISP and upstream is load balanced by the WAN load balancing
**Problem:**
When IPv6 is enabled on multiple PPPoE interfaces the default gateway for IPv6 is rejected by Zebra and no IPv6 connectivity is possible.
Bringing down a single PPPoE Interface or removing IPv6 configuration from one results in the route being installed successfully.
Removing wan load balancing configuration has no effect, the IPv6 routes are always rejected.
IPv6 addresses on the interfaces are link local but do have the same gateway as each other. I have also tried the same setup with PD enabled and non link-local addresses assigned to the interfaces.
**Relevant Config:**
```
pppoe pppoe0 {
authentication {
password ****************
username ****************
}
description AAISP-1
dhcpv6-options {
}
ip {
adjust-mss 1452
}
ipv6 {
address {
autoconf
}
adjust-mss 1432
}
mtu 1492
source-interface eth0.201
}
pppoe pppoe1 {
authentication {
password ****************
username ****************
}
description AAISP-2
dhcpv6-options {
}
ip {
adjust-mss 1452
}
ipv6 {
address {
autoconf
}
adjust-mss 1432
}
mtu 1492
source-interface eth0.202
}
```
**Version:**
```
vyos@router:~$ show version
Version: VyOS 1.5-rolling-202409120007
Release train: current
Release flavor: generic
Built by: autobuild@vyos.net
Built on: Thu 12 Sep 2024 00:07 UTC
Build UUID: ab6885a1-1970-4021-a315-dbbce3831676
Build commit ID: 55c17f9283f32d
Architecture: x86_64
Boot via: installed image
System type: bare metal
Hardware vendor: Dell Inc.
Hardware model: PowerEdge R210 II
Hardware S/N: DXGH9X1
Hardware UUID: 4c4c4544-0058-4710-8048-c4c04f395831
Copyright: VyOS maintainers and contributors
```
**Vtysh:**
```
vyos@router:~$ vtysh
Hello, this is FRRouting (version 9.1.1).
Copyright 1996-2005 Kunihiro Ishiguro, et al.
router# show run
Building configuration...
Current configuration:
!
frr version 9.1.1
frr defaults traditional
hostname router
log syslog
log facility local7
service integrated-vtysh-config
!
ip route 0.0.0.0/0 pppoe0 tag 210 210
ip route 0.0.0.0/0 pppoe1 tag 210 210
ipv6 route ::/0 pppoe0 tag 210 210
ipv6 route ::/0 pppoe1 tag 210 210
ipv6 route [REMOVED]::/56 [REMOVED]::2
!
rpki
exit
!
end
```
**Routes:**
```
vyos@router:~$ show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
T - Table, v - VNC, V - VNC-Direct, A - Babel, F - PBR,
f - OpenFabric,
> - selected route, * - FIB route, q - queued, r - rejected, b - backup
t - trapped, o - offload failure
S>* 0.0.0.0/0 [210/0] is directly connected, pppoe0, weight 1, 00:08:38
* is directly connected, pppoe1, weight 1, 00:08:38
vyos@router:~$ show ipv6 route
Codes: K - kernel route, C - connected, S - static, R - RIPng,
O - OSPFv3, I - IS-IS, B - BGP, N - NHRP, T - Table,
v - VNC, V - VNC-Direct, A - Babel, F - PBR,
f - OpenFabric,
> - selected route, * - FIB route, q - queued, r - rejected, b - backup
t - trapped, o - offload failure
S>r ::/0 [210/0] is directly connected, pppoe0, weight 1, 00:08:41
r is directly connected, pppoe1, weight 1, 00:08:41
```
**Log Output:**
```
Nov 12 13:45:32 router zebra[1492]: [HSYZM-HV7HF] Extended Error: IPv6 routes can not use an IPv4 nexthop
Nov 12 13:45:32 router zebra[1492]: [WVJCK-PPMGD][EC 4043309093] netlink-dp (NS 0) error: Invalid argument, type=RTM_NEWROUTE(24), seq=367, pid=3533212616
Nov 12 13:45:32 router zebra[1492]: [VYKYC-709DP] default(0:254):::/0: Route install failed
```