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CASA C2200 TFTP reply never forwarded to Cable Modem

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CASA C2200 TFTP reply never forwarded to Cable Modem


I have a basic lab setup everything on the same subnet.

GigE 0
Cable Modem
Defined IP bundle on CASA (unassigned IP address)


DHCP works fine IP client is assigned to the cable modem
TFTP is sent from towards but when the data is sent back the TFTP server cannot find the CM

Is this clear?

I'm not sure if it's a routing issue since all my servers/devices are on the same subnet. I think the CMTS is unable to route since everything is on the same subnet. Is there a easy solution for this?


Casa is a router so you need

Casa is a router so you need to set different subnet for CM


Casa is a router so you need

Is it possible for CASA to not behave as a router? so that CASA behaves as a bridge of sorts?

no, cmts casa is a router

no, cmts casa is a router like every "big/new" cmts (arris c4, cisco ubr)

The only way to bridge is to

The only way to bridge is to setup either the CM or CPE as a VPN. The CMTS is unable to bridge is my understanding.

Casa Update

Sorry for the late reply, the problem was resolved by creating a new subnet and placing both CM&CPEs on the same subnet, now looking at splitting the CMs and CPEs on different subnets as follows:

192.25.10.xx CM subnet
192.25.11.xx CPE subnet

interface ip-bundle 1
ip address
ip address secondary

Yet what happens is the CM boots up ok DHCP& TFTP obtaining the config file fine, yet the CPE obtains the IP address but no TFTP is sent by the CPE to download the configuration file. I'm not sure if I need to make configuration changes to the docsismac or maybe can it be a DHCP option that is incorrectly set?

interface docsis-mac 1
no shutdown
sync-interval 10
insertion-interval 20
ucd-interval 1000
no dhcp-authorization
invited-ranging-attempts 16
ip-provisioning-mode ipv4-only
no early-authentication-encryption
no extended-upstream-frequency-range
cm-status event report
downstream channel bonding
upstream channel bonding
no tftp-proxy
no upstream drop classifier
no send udc rules
no dhcp-giaddr-primary
no dhcp-insert
mdd interval 2000
sid-cluster max-requests 0
sid-cluster max-outstanding-bytes 0
sid-cluster max-total-bytes 0
sid-cluster max-time 0
max sid-cluster per-service-flow 2
ip bundle 1
downstream 1 interface qam 0/0/0
downstream 2 interface qam 0/0/1
downstream 3 interface qam 0/0/2
downstream 4 interface qam 0/0/3
upstream 1 interface upstream 1/0/0
mgmd ipv4 query-interval 125
mgmd ipv4 version 3
mgmd ipv4 max-query-response-time 100
mgmd ipv4 proxy-interface gige 0
mgmd ipv4 robustness 2
mgmd ipv4 last-member-query-interval 10
no mgmd ipv4 shutdown
mgmd ipv6 query-interval 125
mgmd ipv6 version 2
mgmd ipv6 max-query-response-time 100
mgmd ipv6 proxy-interface gige 0
mgmd ipv6 robustness 2
mgmd ipv6 last-member-query-interval 10
mgmd ipv6 shutdown
privacy kek life-time 604800
privacy tek life-time 43200
no cable cm-status report event-list 1,2,3,4,5,6,7,8,9,10
no cm trap
cm trap interval 600
max cpes 0


if your using DHCPD what you

if your using DHCPD what you probably need is a shared-network. A shared-network treats requests from either subnet as if they came from the same subnet. If the casa cmts is anything like a cisco, cpe dhcp requests are received from the primary ip on the cable bundle (because it is forwarding them from the cpe/CM). If you don't have the cpe subnet and the cm subnet in a shared network you will end up with one or the other giving you a no free leases found in the logs.

if your using a different dhcp server consult the docs for whatever they have that is similar to a shared-network.

Even when configuring the

Even when configuring the DHCPD server with shared network the same result, unless I made a error in the shared-network configuration. The UBEE CM comes up but the CPE never retrieves the configuration. I'm not sure if the TFTP request is generated or not forward out of the CASA CMTS. (DVM2210)

Ah with CASA the DHCP requests are received with the 192.25.11.xx subnet unless I disable the no dhcp-giaddr-primary, either way the CM boots up but not the CPE.


TFTP Reply


Perhaps I missed the detail in the thread but what is this CPE device that needs a tftp file?

Hi. the device is a

Hi. the device is a AMBIT654-11 (UBEE) DVM2210 EDVA so the CM obtains a config file and then the CPE (TEL1 & TEL2 internal) obtains a configuration file also.


I noticed in your config of

I noticed in your config of your "blade" or whatever casa calls them you have

no tftp-proxy

Have you tried enabling the tftp=proxy?

Actually you can set bridge

Actually you can set bridge mode for CPE configuring L2VPN


I setup a different subnet

I setup a different subnet today but yet still not working properly, the DHCP discover is received by the DHCP but no response by the DHCP server. From the traces it looks like the Gige interface is asking who has the DHCP server IP address and tell the gige interface. I'll have to review the configuration.

Hi, please post your config


please post your config (show run) here.
Seems like a routing issue. Do you have configured a default route?

Normal you configure a ip bundle like:

interface ip-bundle 1
ip address
ip address secondary
ip address secondary

First is primary and for the CMs.
Second is for MTAs and third for CPEs.

In your docsis mac you have to map this bundle:

interface docsis-mac 1
description "all-in-MAC"
no shutdown
no dhcp-authorization
no early-authentication-encryption
no tftp-proxy
ip bundle 1

Then you should us a default route:
route net 0 gw

This are examples of course.



I was wondering if the UBEE

I was wondering if the UBEE configuration file was somehow restricting the MTA from being on a different subnet.

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