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cisco cmts pppoe client not reacble from outside

hi all experts

i have a very wierd problem. i have a cisco router ubr 7246 with cable modems connected. the cable modems are also from cisco ubr920. customer connect their PCs to the cable modems. i have pppoe over cable configured on router ubr7246. pppoe is successful and the customers are assigned public IPs from the radius server. customer can ping to the router and the router is able to ping to the customer ip. but customer cannot ping to any other ip beyond the router.

when i trace to the customer ip , the trace reaches to the router ubr7246 and times out after that. when i do a "show ip route customer_ip" from the neighbor routers of the ubr7246, the route is seen to be coming from the ubr7246. but still i cannot ping to the customer ip.

when i clear route in ubr7246 then one single ping takes place and times out after that. when i clear ospf in ubr7246 same thing happens. just one ping. when i do a continuous ping to that ip and then only establish the pppoe session, the same thing happens. one single instance of ping happens when the pppoe is established and then nothing after that.

so while troubleshooting i moved pppoe from cable to ethernet interface. the customer ip could be pinged when the pppoe is done on the ethernet interface.

its very baffling. is there some special command to be added when pppoe is done over cable interface? is it a pppoe problem or a routing problem i am not able to understand...

shekhar basnet
Avatar of shekharbasnet


some relevant config

ip dhcp smart-relay
ip dhcp relay information option
ip dhcp pool cm-platinum
   option 7 ip
   option 4 ip
   option 2 hex ffff.8f80
   lease 7 0 10
vpdn enable
no vpdn logging
vpdn-group gyanu
  protocol pppoe
  virtual-template 10
 lcp renegotiation always
interface Loopback0
 ip address x.x.x.140
 no ip route-cache
 no ip mroute-cache
interface Loopback10
 ip address
interface Loopback50
 no ip address
interface FastEthernet0/0
 ip address x.x.x.239
 ip ospf message-digest-key 1 md5 xxxxxxxxx
interface Cable3/0
 ip address
 no keepalive
 cable downstream annex B
 cable downstream modulation 64qam
 cable downstream interleave-depth 32
 cable downstream frequency 476000000
 cable upstream 0 frequency 23008000
 cable upstream 0 power-level 0
 cable upstream 0 power-adjust continue 15
 cable upstream 0 modulation-profile 3
 no cable upstream 0 shutdown
 no cable upstream 1 shutdown
 no cable upstream 2 shutdown
 cable upstream 3 shutdown
 cable upstream 4 shutdown
 cable upstream 5 shutdown
 cable helper-address cable-modem
 pppoe enable
interface Virtual-Template10
 ip unnumbered Loopback10
 ip mtu 1492
 no peer default ip address
 ppp authentication pap
router ospf 1
 area 0 authentication message-digest
 redistribute connected subnets
 redistribute static subnets
 network x.x.x.140 area 0
 network x.x.x.239 area 0
 distribute-list prefix myprefix out
ip classless
no ip http server
ip tacacs source-interface Loopback0
ip ospf name-lookup
ip prefix-list myprefix seq 5 permit x.x.224.0/19 ge 20
never mind.
after adding "ip cef" to the router, everything is normal and working fine.
mod pls close and refund.
Avatar of EE_AutoDeleter

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shekharbasnet  Do you still operate a Cisco UBR7246?  I too am trying to do an ucommon PPPoE service over docsis, and could use some pointers if you have any.

Currently I'm trying too see if any radius attributes can control speeds at the  PPPoE layer instead of customizing the cable modem.   Trying a generic cable modem configuration approach, and control the rest within PPPoE.

Anyone else with input greatly appreciated as well.