# IPv6 routing issues -> high packet loss



## GizahNL (May 29, 2015)

tldr.: LAN interface has two virtual IPv6 subnets, subnet to subnet communication results in high packet loss.

So I've got a /56 delegated to me by my ISP which I have subdivided into a few subnets. 

My FreeBSD firewall box has two physical interfaces (LAN and WAN)  and a tun interface for 6rd (managed by u6rd).

The LAN interface has two IPv6 public addresses both configured as /64 on different subnets:
	
	



```
re0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
   options=8209b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,WOL_MAGIC,LINKSTATE>
   ether 00:01:2e:50:4b:d2
   inet 10.168.0.1 netmask 0xfffffe00 broadcast 10.168.1.255
   inet6 fe80::201:2eff:fe50:4bd2%re0 prefixlen 64 scopeid 0x1
   inet6 xxxx:xxxx:xx07:a001::1 prefixlen 64
   inet6 xxxx:xxxx:xx07:a002::1 prefixlen 64
   nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
   media: Ethernet autoselect (1000baseT <full-duplex>)
   status: active
```
The first subnet is for static clients, basically all my servers running on a separate box as jails (network is bridged on that box and I use vimage and epair).

The second subnet is managed by rtadvd with the following configuration:
	
	



```
re0:\
   :addrs#1:addr="xxxx:xxxx:xx07:a002::1":prefixlen#64:tc=ether:
```
The firewall box is able to reach all nets perfectly, also access from inside the nets to either internet or subnets configured on the tun interface as aliases works fine. 
The problem arises when I try to access from one subnet to another, this results in packetloss of typically 25-75% at seemingly random, usually after some time of pinging the packet loss dissipates completly as if the firewall has learned that it should route. 
Any idea of what could be the causes?


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