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Static IPs, IPv6 and ASUS RT-AC87U router....


Static IPs, IPv6 and ASUS RT-AC87U router....

We have a (supported) SMC business gateway with several static IPv4 addresses.


On the front end network, connected to the SMC through a switch, are our web server etc., which have both static public IPv4 (75.* network) vaddresses as well as a mixture of static & dynamic IPv4's (10.*  frontend network) assigned by DHCP. Also present is an ASUS RT-AC87U router, which has an address on the 10. frontend tnetwork, and which provides addresses to the internal 192.* network via DHCP.


A couple of weeks ago, after an update of the SMC by Comcast, there now is IPv6 working -- at least from systems on the front end network, including the shell of the ASUS router, which can ping -6, access systems on the public IPv6 network.


However, although the ASUS gets (stateful) configuration via DHCPv6, including even a different /64 prefix designation for the internal LAN, which it happily provides via stateful autoconfiguration to the internal network, the internal network systems are unable to access or ping -6 systems on the public network.


The current running theory is that either the SMC or something upstream is not routing the /64 addresses that the internal network is receiving.


The SMC WAN settings from the gatewa are:

WAN DHCP IPv6 Address2001:558:600a:2b:3140:8e12:584c:feb2/64
WAN DHCP IPv6 DNS (primary)2001:558:feed::1
WAN DHCP IPv6 DNS (secondary)2001:558:feed::2


The Front-end LAN gets these settings:

LAN IPv6 Settings

LAN Gateway IPv6 Address2601:600:8100:6700::1/64
LAN IPv6 DNS (primary)2001:558:feed::1
LAN IPv6 DNS (secondary)2001:558:feed::2
LAN IPv6 Address Lifetime (minutes)10080
LAN IPv6 Prefixs Delegations



LAN IPv6 Address:2601:600:8100:6700::1/64
Link-Local Address: fe80::ba9b:c9ff:fedd:58b6

The ASUS shows the following:


IPv6 Configuration
IPv6 Connection Type: Native with DHCP-PD
WAN IPv6 Address: 2601:600:8100:6700:aa1a:99d7:c8f1:9574
WAN IPv6 Gateway: fe80::ba9b:c9ff:fedd:58b6
LAN IPv6 Address: 2601:600:8100:67ff::1/64
LAN IPv6 Link-Local Address: fe80::3a2c:4aff:feaa:c8d0/64
DHCP-PD Enabled
LAN IPv6 Prefix: 2601:600:8100:67ff::/64
DNS Address: 2001:558:feed::2, 2001:558:feed::1


So, it does look like the ASUS is configured to route traffic originating from the internal LAN to the SMC via its link-local address as expected -- thus the conclusion that either the SMC or something upstream is dropping the traffic.





Forum Contributor

Re: Static IPs, IPv6 and ASUS RT-AC87U router....

The SMC does not support prefix delegation.  All of the primitives are there in the configuration but it don't work.


In addition you will notice if you start paying close attention to the SMC that once you activated IPv6 and started trying to use it, the SMC will reboot every 6-8 hours.


the SMC also does not have as many channels available in it as the Netgear and Cisco BWGs do, so in locations that have a lot of customers you may run up against some contention.  That is why Comcast isn't supplying these modems anymore to new business customers.


Call Comcast and have them replace the modem with a Netgear.


Re: Static IPs, IPv6 and ASUS RT-AC87U router....

So Comcast came out yesterday and replaced the SMC because it was failing anyway. I specifically asked them to replace it with a modem that works with IPv6 -- and they ended up putting in the Cisco 3939B -- which does the same behavior as the SMC (no IPv6 for the LAN).


So now I need to call them again and have them swap this one for a Netgear? Are they going to charge me for that?



Forum Contributor

Re: Static IPs, IPv6 and ASUS RT-AC87U router....

They didn't charge me but that was a few years ago.  In particular since you told them to swap with a Netgear like I told you to do, and they didn't do it, it seems to me the onus is on them to do what you told them to do.

Trusted Forum Contributor

Re: Static IPs, IPv6 and ASUS RT-AC87U router....

FYI, techs are not obligated to give you any specific model of gateway, even if you request it. You get whatever model they happen to have on their truck at the time of visit. I've had SOME success requesting a certain gateway by having the CSR notate it on the trouble ticket, but that's no guarantee.


As far as not getting charged.... technically they can charge for any call that isn't the direct result of Comcast-provided equipment failure. I've heard people having pretty good luck calling in, explaining the situation, and getting the charge removed. YMMV on that.

Forum Contributor

Re: Static IPs, IPv6 and ASUS RT-AC87U router....

Call in to customer support and request a Netgear that is how I did mine.  The customer support rep. had a mechanism for ordering Netgears, they notated it on an SMC order or something like that.  Just ask the customer service rep to ask her boss or another rep.how to do it if she isn't familiar with the process.


Your service IS broken, by the way.  So let's not have any of this nonsense about it not being an equipment failure because it IS an equipment failure.


If you didn't specifically order a Netgear from customer service, then you can't expect the technical support guy to have one in his truck.

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