Regular Visitor
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12 Messages
Xfinity Internet - LoS ( Provisioning and DHCP )
Any insight and understandings from Xfinity would help greatly. I had a week of rough weeking with outages disrupting work and distance learning (3 kids), and I could not gain any further insight from "ComcastCares" . I don't know know what caused the extended outage I experienced, but the intermittent outages were traced to a couple of factors.
Provisioning - I asked up to upgrade my "no longer supported" modem due to intermittent service disruptions before anyone would look at my issue. The replacement is a SBG6782-ACH.
1. Could could explain why I was able to (re)provision the modem the first time via the self-help portal but no longer can?
2. What restricts the SBG6782-AC from operating in Routed/Bridged Mode. Placing an exception by MAC for bridge mode does not work either. The router cannot successfully obtain a lease when under this bridge mode configuration. Do we need a firmware change or DHCP server configuration change?
The end goal here is finding a way to forward syslog messages to the router and perhaps allow clients to continue to work (distance learning and telecommuting) when the router cannot obtain a DHCP lease.
DHCP - Causing random connectivity issues with unexpected DHCP behaviors
1. Can you explain the configurations around your DHCP services?
Release does not seem to work. The DHCP client gets back the same IP address which is okay but the lease time always continues to count down. Some info is with the log snippets below. Are there configurations prohibiting when lease renews would work?
udhcpc is installed by the router vendor and is tied into scripts that under DHCP failures can cause the router to restart services or the router itself causing longer service interuptions. Please share if there are specific parameters the client should be running with.
Mar 9 00:34:54rtr udhcpc[8859]: started, v1.25.1 Mar 9 00:34:54 rtr udhcpc[8859]: sending discover Mar 9 00:34:54 rtr udhcpc[8859]: sending select for 73.33.132.180 Mar 9 00:34:54 rtr udhcpc[8859]: lease of 73.33.132.180 obtained, lease time 321927 Mar 9 00:34:54 rtr rc_service: udhcpc 8899:notify_rc start_dhcp6c Mar 9 00:35:00 rtr rc_service: udhcpc 8899:notify_rc stop_pptpd Mar 9 00:35:02 rtr rc_service: udhcpc 8899:notify_rc start_pptpd Mar 9 00:35:02 rtr rc_service: waitting "stop_pptpd" via udhcpc ... Mar 9 10:20:31 rtr udhcpc-cfg: udhcpc RESTART Mar 9 10:20:31 rtr udhcpc[13638]: unicasting a release of 73.33.132.180 to 76.96.20.213 Mar 9 10:20:31 rtr udhcpc[13638]: sending release Mar 9 10:20:31 rtr udhcpc[13638]: entering released state Mar 9 10:20:31 rtr udhcpc[13638]: received SIGTERM Mar 9 10:20:31 rtr udhcpc[13638]: entering released state Mar 9 10:20:31 rtr udhcpc[18065]: started, v1.25.1 Mar 9 10:20:31 rtr udhcpc[18065]: sending discover Mar 9 10:20:31 rtr udhcpc[18065]: sending select for 73.33.132.180 Mar 9 10:20:31 rtr udhcpc[18065]: lease of 73.33.132.180 obtained, lease time 286789
Perhaps someone at Xfinity can traceback if the two offers were from the same DHCP server or intentional behavior. The logs do offer hints at the release not working in the traditional sense.
XfinityGabriel
Official Employee
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2.1K Messages
4 years ago
Hi, @jackhc88! Thanks for using our Forums page to reach out to Comcast for help with the internet service concern and for your patience! I am sorry to learn about the rough week with those interruptions. I rely on my services for my lively hood so I can understand the frustration that this can cause. We can help! To get started, would you mind sending us a private message by clicking on my handle “ComcastGabe” and confirming your first/last name and address so I can ensure I am working on the correct account?
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jackhc88
Regular Visitor
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12 Messages
4 years ago
@ComcastGabe : Thanks for your concern and reaching out. Instead of reforwarding the last capture snippet, I am generated a fresh hope. I think the lease is past the 50% watermark, and I confirmed the client log lease time matches the packet capture.
I hope this additional info helps. I hope it also rules out the normal connectivity and provisioning concerns which has suffered constant restarts to the modem from the other support guys 😀.
dhcp0.pcap
12:40:20.008926 IP (tos 0x0, ttl 64, id 4982, offset 0, flags [DF], proto UDP (17), length 328) 73.33.132.180.68 > 76.96.20.213.67: [bad udp cksum 0x3050 -> 0xe773!] BOOTP/DHCP, Request from a8:5e:45:f3:06:d8, length 300, xid 0x52cf1875, Flags [none] (0x0000) Client-IP 73.33.132.180 Client-Ethernet-Address a8:5e:45:f3:06:d8 Vendor-rfc1048 Extensions Magic Cookie 0x63825363 DHCP-Message Option 53, length 1: Request Client-ID Option 61, length 7: ether a8:5e:45:f3:06:d8 MSZ Option 57, length 2: 1492 Parameter-Request Option 55, length 10: Subnet-Mask, Default-Gateway, Domain-Name-Server, Hostname Domain-Name, BR, Static-Route, NTP Classless-Static-Route, Classless-Static-Route-Microsoft Vendor-Class Option 60, length 12: "udhcp 1.25.1" Hostname Option 12, length 2: "x1" 12:40:20.037110 IP (tos 0x48, ttl 57, id 22335, offset 0, flags [DF], proto UDP (17), length 338) 76.96.20.213.67 > 73.33.132.180.68: [udp sum ok] BOOTP/DHCP, Reply, length 310, xid 0x52cf1875, Flags [none] (0x0000) Client-IP 73.33.132.180 Your-IP 73.33.132.180 Client-Ethernet-Address a8:5e:45:f3:06:d8 Vendor-rfc1048 Extensions Magic Cookie 0x63825363 DHCP-Message Option 53, length 1: ACK Server-ID Option 54, length 4: 76.96.20.213 Lease-Time Option 51, length 4: 278401 Subnet-Mask Option 1, length 4: 255.255.252.0 Default-Gateway Option 3, length 4: 73.33.132.1 Domain-Name-Server Option 6, length 8: 75.75.75.75,75.75.76.76 Domain-Name Option 15, length 20: "hsd1.nj.comcast.net." BR Option 28, length 4: 255.255.255.255 Hostname Option 12, length 2: "x1" 12:40:33.577292 IP (tos 0x0, ttl 64, id 14200, offset 0, flags [DF], proto UDP (17), length 328) 73.33.132.180.68 > 76.96.20.213.67: [bad udp cksum 0x3050 -> 0xe773!] BOOTP/DHCP, Request from a8:5e:45:f3:06:d8, length 300, xid 0x52cf1875, Flags [none] (0x0000) Client-IP 73.33.132.180 Client-Ethernet-Address a8:5e:45:f3:06:d8 Vendor-rfc1048 Extensions Magic Cookie 0x63825363 DHCP-Message Option 53, length 1: Request Client-ID Option 61, length 7: ether a8:5e:45:f3:06:d8 MSZ Option 57, length 2: 1492 Parameter-Request Option 55, length 10: Subnet-Mask, Default-Gateway, Domain-Name-Server, Hostname Domain-Name, BR, Static-Route, NTP Classless-Static-Route, Classless-Static-Route-Microsoft Vendor-Class Option 60, length 12: "udhcp 1.25.1" Hostname Option 12, length 2: "x1" 12:40:33.604476 IP (tos 0x48, ttl 57, id 25121, offset 0, flags [DF], proto UDP (17), length 338) 76.96.20.213.67 > 73.33.132.180.68: [udp sum ok] BOOTP/DHCP, Reply, length 310, xid 0x52cf1875, Flags [none] (0x0000) Client-IP 73.33.132.180 Your-IP 73.33.132.180 Client-Ethernet-Address a8:5e:45:f3:06:d8 Vendor-rfc1048 Extensions Magic Cookie 0x63825363 DHCP-Message Option 53, length 1: ACK Server-ID Option 54, length 4: 76.96.20.213 Lease-Time Option 51, length 4: 278387 Subnet-Mask Option 1, length 4: 255.255.252.0 Default-Gateway Option 3, length 4: 73.33.132.1 Domain-Name-Server Option 6, length 8: 75.75.75.75,75.75.76.76 Domain-Name Option 15, length 20: "hsd1.nj.comcast.net." BR Option 28, length 4: 255.255.255.255 Hostname Option 12, length 2: "x1"0
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jackhc88
Regular Visitor
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12 Messages
4 years ago
I tested ISC's dhclient and picked some clues.
DHCPACKs are randomly bouncing between two IPs, 96.120.75.1 and 73.33.132.1. Maybe infrastructure guys can see if they can restrict it to the IP facing the customer, 73.33.132.1.
Server is consistently 76.96.20.213. Leases are still not honored with the new DHCP client. I did noticed there appears to be two different timers on the lease expiration identified as
76.96.20.213.
Please let me know if release/renew is broken by design.
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jackhc88
Regular Visitor
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12 Messages
4 years ago
@ComcastLysaP , @ComcastJosephB @ComcastGabe , @ComcastJeniece : It appears with the new web portal, private messages is broken for me. I am going to attempt to reply here.
@ComcastGabe: All the DHCP observations still point to issues with release and renew. I swapped out the binary the router vendor uses, udhcpc, with ISC's dhclient. So far, the router stays up with all the DHCP errors as the ISC versions is able to ignore the DHCP errors. The only problem is that the binary is now managing six different leases with the same information other than timestamps. It will likely continue to rise. I would imagine the DHCP service will see unnecessary renew requests until the issue is fixed on Xfinity's end and tax everyone's system. As for customers that use udhcpc and run into the DHCP service issues such as I have, they will continue to experience disruptions.
@ComcastLysaP : If the modem is bridge modem and receives a DHCP address, should the router that is in bridge mode also be assigned a DHCP address?
I can understand that your support demarcation ends at the modem, but the issue not a layer 2 issue. What I would like is for someone to to check to see why the request from the router is rejected. Unless, there is a modem firmware managed by Xfinity is available that enables wifi and syslog features in bridge mode which Xfinity enables in "routed" mode.
@ComcastJosephB : Let me know if you need more info from me on the provisioning issue.
@ComcastJeniece : The screenshot on the provisioning issue occurs after a while after filling in the HFC MAC address.
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jackhc88
Regular Visitor
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12 Messages
4 years ago
@ComcastValerie : If you could escalate these two issues internally at xfinity and respond back, that would be appreciated. I don't think any more information from my end would be helpful. These issues should be easily reproduced at xfinity. My guess is that this is probably by design by xfinity which is causing these headaches for users ands support people. By finding a workaround for the xfinity DHCP issue, my gear has been stable for over a ten day stretch rather than randomly losing connectivity throughout the work day due to DHCP failures. If you do need more insight, please feel free to call me.
Hopefully, the info you share in this post will help other users.
(edited)
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