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SP2
New Member

Unable to ping router IP across a VLAN but responding to broadcast ping

I need some troubshooting help to solve this issue. We have 2 managed routers "A" and "B"across the service privder's VLAN network. The set up is like this->

Router A---VLAN "X"--> ISP ATM Switch A<----->ISP ATM Backbone<-----> ISP ATM Switch B<--VLAN "X"---Router B

We are able to ping from Router A to Router B on VLAN X with few drops but can't ping the other way around at all. The rest of the VLANs(there is 1 more) on the same trunk which is working just fine. So we opened an investigation with ISP to check for specefic VLAN having issue. The ISP claims that they are able to ping from their ATM switch A to our Router B with no drops but can't ping our Router "A" IP address. But if they do ping the broadcast IP they get response from Routers A and B both which kinda puzzles me as why would Router A will respond to broadcast IP if it does not respond to its IP ? Any ideas , please help..Thanks!

6 REPLIES
Green

Unable to ping router IP across a VLAN but responding to broadca

Hi,

Can you show at least the interface configs for both routers A & B

Regards

Alex

Regards, Alex. Please rate useful posts.
SP2
New Member

Unable to ping router IP across a VLAN but responding to broadca

Hi acampbell,

I have pasted the int configs for both routers A and B respectively below. Any help will be appreciated in diagnosing this issue as ISP now wants to install a switch in front of our routerA and put sniffer on it for diagnostics. This will have a 15 min. downtime on all our VLANS on RouterA  which are catering multiple sites on this trunk (as this is a primary hub router) with few sites having no back up at all

Thanks for your help!

RouterA#sh int gigabitEthernet 0/0.209
GigabitEthernet0/0.209 is up, line protocol is up
  Hardware is Pinnacle GE, address is 001a.6ccd.0300 (bia 001a.6ccd.0300)
  Description: --- To RouterB
  Internet address is x.x.x.145/28
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 6/255, rxload 4/255
  Encapsulation 802.1Q Virtual LAN, Vlan ID  209.
  ARP type: ARPA, ARP Timeout 04:00:00
  Keepalive set (10 sec)
  Last clearing of "show interface" counters never
RouterA#sh ip int gigabitEthernet 0/0.209
GigabitEthernet0/0.209 is up, line protocol is up
  Internet address is x.x.x.145/28
  Broadcast address is 255.255.255.255
  Address determined by setup command
  MTU is 1500 bytes
  Helper address is not set
  Directed broadcast forwarding is disabled
  Outgoing access list is not set
  Inbound  access list is not set
  Proxy ARP is enabled
  Local Proxy ARP is disabled
  Security level is default
  Split horizon is enabled
  ICMP redirects are always sent
  ICMP unreachables are always sent
  ICMP mask replies are never sent
  IP fast switching is enabled
  IP Flow switching is disabled
  IP CEF switching is enabled
  IP CEF switching turbo vector
  IP CEF turbo switching turbo vector
  VPN Routing/Forwarding "znet"
  IP multicast fast switching is enabled
  IP multicast distributed fast switching is disabled
  IP route-cache flags are Fast, CEF
  Router Discovery is disabled
  IP output packet accounting is disabled
  IP access violation accounting is disabled
  TCP/IP header compression is disabled
  RTP/IP header compression is disabled
  Probe proxy name replies are disabled
  Policy routing is disabled
  Network address translation is disabled
  WCCP Redirect outbound is disabled
  WCCP Redirect inbound is disabled
  WCCP Redirect exclude is disabled
  BGP Policy Mapping is disabled
RouterA#

RouterB#sh int fastEthernet 0/0.209
FastEthernet0/0.209 is up, line protocol is up
  Hardware is MV96340 Ethernet, address is 001f.9e17.8218 (bia 001f.9e17.8218)
  Description: --- To RouterA
  Internet address is x.x.x.146/28
  MTU 1500 bytes, BW 10000 Kbit/sec, DLY 1000 usec,
     reliability 255/255, txload 7/255, rxload 12/255
  Encapsulation 802.1Q Virtual LAN, Vlan ID  209.
  ARP type: ARPA, ARP Timeout 04:00:00
  Last clearing of "show interface" counters never
RouterB#sh ip int fastEthernet 0/0.209
FastEthernet0/0.209 is up, line protocol is up
  Internet address is x.x.x.146/28
  Broadcast address is 255.255.255.255
  Address determined by setup command
  MTU is 1500 bytes
  Helper address is not set
  Directed broadcast forwarding is disabled
  Outgoing access list is not set
  Inbound  access list is not set
  Proxy ARP is enabled
  Local Proxy ARP is disabled
  Security level is default
  Split horizon is enabled
  ICMP redirects are always sent
  ICMP unreachables are always sent
  ICMP mask replies are never sent
  IP fast switching is enabled
  IP fast switching on the same interface is enabled
  IP Flow switching is enabled
  IP CEF switching is enabled
  IP CEF VPN Flow Fast switching turbo vector
  VPN Routing/Forwarding "znet"
  IP multicast fast switching is enabled
  IP multicast distributed fast switching is disabled
  IP route-cache flags are Fast, Flow cache, CEF, Subint Flow
  Router Discovery is disabled
  IP output packet accounting is disabled
  IP access violation accounting is disabled
  TCP/IP header compression is disabled
  RTP/IP header compression is disabled
  Policy routing is disabled
  Network address translation is disabled
  BGP Policy Mapping is disabled
  WCCP Redirect outbound is disabled
  WCCP Redirect inbound is disabled
  WCCP Redirect exclude is disabled
RouterB#

Green

Unable to ping router IP across a VLAN but responding to broadca

These look OK to me.

What about the switch ports the routers are connected to.

Router A x.x.x.145/255.255.255.240 Encap Dot1Q 209

Router B x.x.x.146/255.255.255.240 Encap Dot1Q 209

Subnet x..x.x.144/255.255.255.240

Regards

Alex

Regards, Alex. Please rate useful posts.
SP2
New Member

Unable to ping router IP across a VLAN but responding to broadca

I have no access to Switch as its service provider side on both ends(A & B)

Bronze

Unable to ping router IP across a VLAN but responding to broadca

Hi Nitin,

You said, you get response when pinged to broadcast ip,

is the ip they ping is x.x.x.159 or which ip ???

SP2
New Member

Unable to ping router IP across a VLAN but responding to broadca

Hi Manju- Yes, when they ping x.x.x.159 from their switch, they get response from both .145(RouterA) and .146(Router B) But when pinged from RouterA to RouterB, we have 60-80% success and no response when pinged from RouterB to RouterA.

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