Two BT lines and ipv6

ipc6023 — Tue, 21 Nov 2023 17:08:42 GMT

Hello I've asked about this before and got a deafening silence.

Okay since my last post I've upgraded to fibre. This goes via two openreach modems to a draytek 3910. Fibre is on wan5 and wan 6

So two BT fibre connections and the 3910 only will connect with ipv6 on one line at any time.

If I disable one wan the ipv6 comes up on the other wan so ipv6 is certainly available on both lines.

You can see the router requesting an ipv6 address on wan 5 via dhcp but it's timing out.

Draytek are checking things out at their end but think the issue is with BT.

"2023-11-21 16:59:24", "[DHCPv6c] Send solicit to FF02::1:2 on WAN5"

"2023-11-21 16:59:23", "[DHCPv6c] Send solicit to FF02::1:2 on WAN5"

"2023-11-21 16:59:23", "[DHCPv6c] Send release message (WAN5, len=87)"

"2023-11-21 16:59:22", "[IPv6] IPv6 event timeout (RA, 15 sec)!"

"2023-11-21 16:59:22", "[IPv6] WAN5, Type(PPP), Rx EVENT = EVT_TIME_OUT"

"2023-11-21 16:59:20", "WAN5 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x12 Magic Number: 0x0 00 00 ##"

"2023-11-21 16:59:20", "WAN5 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x12 Magic Number: 0x2b3e 92 76 ##"

"2023-11-21 16:59:16", "WAN6 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x1B Magic Number: 0x0 00 00 ##"

"2023-11-21 16:59:16", "WAN6 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x1B Magic Number: 0x26ed 08 e2 ##"

"2023-11-21 16:59:09", "WAN5 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x11 Magic Number: 0x0 00 00 ##"

"2023-11-21 16:59:09", "WAN5 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x11 Magic Number: 0x2b3e 92 76 ##"

"2023-11-21 16:59:08", "[IPv6] IPv6 event timeout (DHCPv6, 15 sec)!"

"2023-11-21 16:59:08", "[IPv6] WAN5, Type(PPP), Rx EVENT = EVT_TIME_OUT"

"2023-11-21 16:59:06", "WAN6 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x1A Magic Number: 0x0 00 00 ##"

"2023-11-21 16:59:06", "WAN6 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x1A Magic Number: 0x26ed 08 e2 ##"

"2023-11-21 16:59:04", "statistic: Session Usage: 65 (5 min average)"

"2023-11-21 16:59:04", "statistic: WAN6: Tx 27 Kbps, Rx 19 Kbps (5 min average)"

"2023-11-21 16:59:04", "statistic: WAN5: Tx 247 Kbps, Rx 162 Kbps (5 min average)"

"2023-11-21 16:59:01", "[DHCPv6c] Send solicit to FF02::1:2 on WAN5"

"2023-11-21 16:58:57", "WAN5 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x10 Magic Number: 0x0 00 00 ##"

"2023-11-21 16:58:57", "WAN5 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x10 Magic Number: 0x2b3e 92 76 ##"

"2023-11-21 16:58:56", "[DHCPv6c] Send solicit to FF02::1:2 on WAN5"

"2023-11-21 16:58:55", "WAN6 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x19 Magic Number: 0x0 00 00 ##"

"2023-11-21 16:58:55", "WAN6 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x19 Magic Number: 0x26ed 08 e2 ##"

"2023-11-21 16:58:54", "[DHCPv6c] Send solicit to FF02::1:2 on WAN5"

"2023-11-21 16:58:53", "[DHCPv6c] Send solicit to FF02::1:2 on WAN5"

"2023-11-21 16:58:53", "[DHCPv6c] Send release message (WAN5, len=87)"

"2023-11-21 16:58:53", "[IPv6] IPv6 event timeout (RA, 15 sec)!"

"2023-11-21 16:58:53", "[IPv6] WAN5, Type(PPP), Rx EVENT = EVT_TIME_OUT"

"2023-11-21 16:58:51", "[DHCPv6s] Send reply to FE80::20A:CDFF:FE38:EEF1 on LAN1"

"2023-11-21 16:58:51", "[DHCPv6] Elapsed time: 65535"

"2023-11-21 16:58:51", "[DHCPv6] Requested option: domain search list"

"2023-11-21 16:58:51", "[DHCPv6] Requested option: DNS"

"2023-11-21 16:58:51", "[DHCPv6] Client DUID: 00:03:00:01:00:0a:cd:38:ee:f1"

"2023-11-21 16:58:51", "[DHCPv6s] Received information request from FE80::20A:CDFF:FE38:EEF1 on LAN1"

"2023-11-21 16:58:46", "WAN5 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x0F Magic Number: 0x0 00 00 ##"

"2023-11-21 16:58:46", "WAN5 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x0F Magic Number: 0x2b3e 92 76 ##"

"2023-11-21 16:58:43", "WAN6 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x18 Magic Number: 0x0 00 00 ##"

"2023-11-21 16:58:43", "WAN6 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x18 Magic Number: 0x26ed 08 e2 ##"

"2023-11-21 16:58:38", "[IPv6] IPv6 event timeout (DHCPv6, 15 sec)!"

"2023-11-21 16:58:38", "[IPv6] WAN5, Type(PPP), Rx EVENT = EVT_TIME_OUT"

"2023-11-21 16:58:35", "WAN5 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x0E Magic Number: 0x0 00 00 ##"

"2023-11-21 16:58:35", "WAN5 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x0E Magic Number: 0x2b3e 92 76 ##"

"2023-11-21 16:58:33", "WAN6 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x17 Magic Number: 0x0 00 00 ##"

"2023-11-21 16:58:33", "WAN6 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x17 Magic Number: 0x26ed 08 e2 ##"

"2023-11-21 16:58:31", "[DHCPv6c] Send solicit to FF02::1:2 on WAN5"

"2023-11-21 16:58:27", "[DHCPv6c] Send solicit to FF02::1:2 on WAN5"

"2023-11-21 16:58:25", "[DHCPv6c] Send solicit to FF02::1:2 on WAN5"

"2023-11-21 16:58:24", "WAN5 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x0D Magic Number: 0x0 00 00 ##"

"2023-11-21 16:58:24", "WAN5 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x0D Magic Number: 0x2b3e 92 76 ##"

"2023-11-21 16:58:24", "[DHCPv6c] Send solicit to FF02::1:2 on WAN5"

"2023-11-21 16:58:23", "[DHCPv6c] Send release message (WAN5, len=87)"

"2023-11-21 16:58:23", "[IPv6] IPv6 event timeout (RA, 15 sec)!"

"2023-11-21 16:58:23", "[IPv6] WAN5, Type(PPP), Rx EVENT = EVT_TIME_OUT"

"2023-11-21 16:58:21", "WAN6 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x16 Magic Number: 0x0 00 00 ##"

"2023-11-21 16:58:21", "WAN6 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x16 Magic Number: 0x26ed 08 e2 ##"

"2023-11-21 16:58:12", "WAN5 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x0C Magic Number: 0x0 00 00 ##"

"2023-11-21 16:58:12", "WAN5 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x0C Magic Number: 0x2b3e 92 76 ##"

"2023-11-21 16:58:10", "WAN6 PPPoE ==> Protocol:LCP(c021) EchoRep Identifier:0x15 Magic Number: 0x0 00 00 ##"

"2023-11-21 16:58:10", "WAN6 PPPoE <== Protocol:LCP(c021) EchoReq Identifier:0x15 Magic Number: 0x26ed 08 e2 ##"

"2023-11-21 16:58:08", "[IPv6] IPv6 event timeout (DHCPv6, 15 sec)!"

"2023-11-21 16:58:08", "[IPv6] WAN5, Type(PPP), Rx EVENT = EVT_TIME_OUT"

Re: Two BT lines and ipv6

licquorice — Tue, 21 Nov 2023 17:16:28 GMT

Not sure I follow the logic. The problem is clearly with the Draytek. To prove that, use 2 separate routers rather than 2 WAN ports on a single device.

Re: Two BT lines and ipv6

WSH — Tue, 21 Nov 2023 18:35:14 GMT

I can’t say I’m surprised at this. I might have missed your point and I’m not an IPv6 expert by any means, but wouldn’t the two fibre connections provide two different network prefixes?

While theoretically two interfaces can have separate network addresses, I can see your network having all sorts of issues with having two different IPv6 network addresses at the same time. Or am I just being silly?

Re: Two BT lines and ipv6

ipc6023 — Tue, 21 Nov 2023 18:49:45 GMT

Nope you're not being silly.

I found an old cisco router and that seemed to work but I had to enable PD and dual stack under the wan settings otherwise zero ipv6 connection.

Re: Two BT lines and ipv6

WSH — Tue, 21 Nov 2023 19:15:00 GMT

Even with delegation I suspect the problem lies in two different /56. Interestingly, I ended up with two SH2’s when I switched to Digital Voice. While both seem to have the same prefix when I plug them in, that prefix is different for each one.

I suspect Draytek might say it can’t be done. Fascinating. Please keep us posted on what they say.

Re: Two BT lines and ipv6

countrypaul — Tue, 21 Nov 2023 19:42:18 GMT

Have you told Draytek the two lines work if you use an old Cisco router? Be interesting to see what they make of it.

Re: Two BT lines and ipv6

licquorice — Tue, 21 Nov 2023 19:45:30 GMT

Yes, with IPv4, you will have one private address on each device accessed via 2 public addresses. However, with IPv6, there are no private addresses so you would be trying to give each device 2 public addresses.

I presume the Draytek is designed for failover from one WAN to the other rather than load balancing between them.

Re: Two BT lines and ipv6

ipc6023 — Tue, 21 Nov 2023 19:56:29 GMT

I've emailed draytek telling them that it works with the cisco.

Things would be even more interesting if I had two different isp's who both used ipv6.

Re: Two BT lines and ipv6

WSH — Tue, 21 Nov 2023 20:26:25 GMT

So, the test on the Cisco is with two lines from the same ISP.

Do they both produce the same prefix? If they do, I would expect that would work. I don’t see how two different prefixes would. As Licquorice said, it’s usually a redunancy thing. One works at one time.

Re: Two BT lines and ipv6

ipc6023 — Wed, 22 Nov 2023 19:30:01 GMT

I'll have to plug it back in too find out.

Re: Two BT lines and ipv6

ipc6023 — Fri, 24 Nov 2023 17:59:37 GMT

Draytek can't reproduce the issue in the lab which is interesting.

Sent them logs and packet capture

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