Visitor
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2 Messages
DHCPv6-PD /60 delegated but return traffic not routed back.
I’ve tried in-app chat and phone support with no success.
Setup
Hitron CODA56 modem
Xfinity is correctly issuing a DHCPv6-PD /60.
Delegated prefix
2601:1c2:4501:5310::/60
WAN IPv6
2001:558:6025:7a:a491:2a57:3cf5:ea78/128
Symptoms
Packets sourced from the delegated prefix leave my WAN interface (confirmed via tcpdump), but no replies return. WAN-sourced IPv6 traffic (from the /128) works perfectly to the same destinations.
I’ve ruled out local configuration issues through power cycles, IPv6 resets, and verification that forwarding is enabled.
I’m requesting escalation to network engineering / CMTS team to check:
- DHCPv6-PD provisioning and the residential /60 boot file for the modem
- CMTS routing tables for prefix 2601:1c2:4501:5310::/60
- Return path / IPv6 forwarding for the delegated prefix
This is not a local config or modem problem. The prefix is being issued but return traffic for it is not being routed back to my connection.
user_fwd75x
Visitor
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2 Messages
3 hours ago
Additional detail
WAN-source IPv6 works:
But delegated-prefix-source traffic fails:
Packet capture on my router’s WAN interface shows the packets leaving toward Comcast:
No replies return.
I also fully power-cycled the Xfinity modem and router, disabled/re-enabled IPv6 on WAN and LAN, and reacquired the same delegated prefix. The issue persists.
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zandor60657
Contributor
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232 Messages
2 hours ago
What are you using for a router? What are you trying to do with a /60? That gets you 16 subnets. I've been using 5 IPv6 subnets on Comcast for years. 2 for my computers (wifi vs. wired - wifi is more restricted), 1 for gizmos, streaming sticks, IoT, phones, etc., 1 for a guest network, and 1 for my work gear since I work from home part time. Works just fine, though I did have to modify a firewall rule to get the DHCP6 response. My Mikrotik router had a default rule that expected a DHCP response from the same subnet, but Comcast was sending from another subnet. You're apparently getting the DHCP6 response, so that's not it.
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