Unable to ping Cisco router

Question

Level 1

20 points

Unable to ping Cisco router

I am setting up some Cisco equipment to do some network testing with. The setup is a switch connected to a router using 802.1q and routing via router on a stick method.

I plug my Mac mini into a port and it auto-negotiates speed and duplex correctly. It gets an IP address (lets say 192.168.2.5) and the proper default gateway information. I can ping the switch but if I try to ping the router (192.168.2.1), I get:

ping: sendto: No route to host
ping: sendto: Host is down
ping: sendto: Host is down
ping: sendto: Host is down
ping: sendto: Host is down

At first I was thinking it was a network problem. But after trying this with my Windows laptop and Linux desktop, I think it's the Mac. Both the Windows and Linux systems can ping all active IP addresses just as they should. It is only the Mac which isn't able to ping the router. But as I said, it can ping the switch so pings probably aren't being filtered on the Mac.

Can anyone offer any suggestions? Thanks a lot!

Mac mini, Mac OS X (10.5.7)

Posted on Jul 29, 2009 6:17 PM

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Answer 1

Dogcow-Moof

Level 8

36,833 points

Jul 29, 2009 7:50 PM in response to kbreit

For some reason your system believes it can't find a route to the router.

Since both IP addresses are on the same subnet, the next thing to check would be to make sure your netmask is properly set.

In most cases for a network like yours it would be 255.255.255.0, but I'm not sure if you're further subnetting the class C network you're playing with, which could result in the problem you cite.

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Answer 2

kbreit Author

Level 1

20 points

Jul 29, 2009 8:20 PM in response to Dogcow-Moof

I did a bit of research and it became a bit more curious during the research. The equipment booted and ifconfig showed:

snip
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
inet 192.168.2.4 netmask 0xffffff00 broadcast 192.168.2.255
*snip

Seems to have proper IP, netmask, and broadcast information. It is a 255.255.255.0 network so this seems to be correct. I pulled 'netmask -r' as well:

Internet:
Destination Gateway Flags Refs Use Netif Expire
default 192.168.2.1 UGSc 2 0 en0
127 localhost UCS 0 0 lo0
localhost localhost UH 4 453 lo0
169.254 link#4 UCS 0 0 en0
192.168.2 link#4 UCS 2 0 en0
192.168.2.1 link#4 UHLW 3 5 en0
192.168.2.2 0:11:92:54:14:41 UHLW 0 2 en0 1180
192.168.2.4 localhost UHS 0 0 lo0
snip

First, what does link#4 mean? Either way, it seems like the interfaces are set up properly. If they aren't (and my routing table is probably the problem) then please let me know. What I do notice is I have the MAC address of the device I can ping but no MAC address of the device I can't ping (2.1).

Then suddenly I notice my Network dialog changes. ifconfig now shows:

snip
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
inet 169.254.117.93 netmask 0xffff0000 broadcast 169.254.255.255
snip

I lost the IP address. No clue why this happened either. It was minutes later so probably too soon for DHCP to expire. Is any of this information I have provided useful? What debugging steps can I take from here?

Message was edited by: kbreit

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Answer 3

Jul 30, 2009 3:36 AM in response to kbreit

Can you also post the interface settings for the windows machine along with the config for the switch and router?

It looks like something going funny with DHCP (since you lose your IP address). Can you try a static IP address and see if that works, that will take some complexity out of the picture.

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Answer 4

Jul 30, 2009 2:25 PM in response to kbreit

Have you enabled 'Portfast' on the switch port that the Mac is connected to. I understand Cisco suggest that all client ports (Windows/Linux/Apple) have this enabled.
see http://www.cisco.com/en/US/products/hw/switches/ps700/productstechnote09186a00800b1500.shtml

My other suggestion is does the Mac have IPv6 enabled and the other clients that work do not?

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Answer 5

kbreit Author

Level 1

20 points

Jul 30, 2009 6:28 PM in response to rack0 tack0

I had enabled portfast before but didn't save. I enabled portfast and it didn't fix things. Thanks for the suggestion though.

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Answer 6

kbreit Author

Level 1

20 points

Jul 30, 2009 6:32 PM in response to Noah Robbin

I had saved the windows settings but they didn't get onto my computer (I think I shut down too fast before Dropbox sync'd). Either way, here is a Linux computer's interface settings. If you really need the Windows settings, let me know.

Setting a static IP didn't help the pinging. Same behavior.

Linux Config:

eth0 Link encap:Ethernet HWaddr 00:1e:ec:d0:06:2d
inet addr:192.168.2.4 Bcast:192.168.2.255 Mask:255.255.255.0
inet6 addr: fe80::21e:ecff:fed0:62d/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:188 errors:0 dropped:0 overruns:0 frame:0
TX packets:260 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:16633 (16.6 KB) TX bytes:35151 (35.1 KB)
Interrupt:250 Base address:0xc000

Router (192.168.2.1):

Current configuration : 2653 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname LabRouter
!
boot-start-marker
boot-end-marker
!
logging message-counter syslog
enable password temporary
!
no aaa new-model
no network-clock-participate wic 2
ip source-route
!
!
ip dhcp excluded-address 192.168.1.1
ip dhcp excluded-address 192.168.2.1
ip dhcp excluded-address 192.168.2.2
ip dhcp excluded-address 192.168.2.3
ip dhcp excluded-address 192.168.3.1
ip dhcp excluded-address 192.168.3.2
ip dhcp excluded-address 192.168.3.3
ip dhcp excluded-address 192.168.1.2
ip dhcp excluded-address 192.168.1.3
!
ip dhcp pool LabDHCP
network 192.168.2.0 255.255.255.0
default-router 192.168.2.1
dns-server 68.87.72.134
!
ip dhcp pool UserDHCP
network 192.168.1.0 255.255.255.0
default-router 192.168.1.1
dns-server 68.87.72.134
!
!
ip cef
no ipv6 cef
multilink bundle-name authenticated
voice-card 0
!
!
!
archive
log config
hidekeys
!
!
controller T1 0/2/0
!
controller T1 0/2/1
!
!
!
!
!
interface FastEthernet0/0
description External Interface
mac-address 0016.cb97.c8a5
ip address dhcp hostname LabRouter
ip nat outside
ip virtual-reassembly
duplex auto
speed auto
interface Service-Engine0/1
no ip address
shutdown
!
interface FastEthernet0/1
description Lab Interface
no ip address
ip virtual-reassembly
duplex auto
speed auto
!
interface FastEthernet0/1.1
encapsulation dot1Q 1 native
ip address 192.168.1.1 255.255.255.0
ip nat inside
ip virtual-reassembly
!
interface FastEthernet0/1.2
encapsulation dot1Q 2
ip address 192.168.2.1 255.255.255.0
ip nat inside
ip virtual-reassembly
!
interface FastEthernet0/3/0
description User Access
!
interface FastEthernet0/3/1
description User Access
!
interface FastEthernet0/3/2
description User Access
!
interface FastEthernet0/3/3
description User Access
!
interface Vlan1
no ip address
!
ip default-gateway 24.7.200.1
ip forward-protocol nd
!
!
no ip http server
ip nat pool overld2 192.168.2.1 192.168.2.255 prefix-length 24
ip nat inside source list 1 interface FastEthernet0/0 overload
!
access-list 1 permit 192.168.1.0 0.0.0.255
access-list 1 permit 192.168.2.0 0.0.0.255
access-list 1 permit 192.168.3.0 0.0.0.255
disable-eadi
!
!
!
control-plane
!
!
!
!
mgcp fax t38 ecm
!
!
!
!
!
line con 0
line aux 0
line 130
no activation-character
no exec
transport preferred none
transport input all
transport output pad telnet rlogin lapb-ta mop udptn v120
line vty 0 4
password temporary
login
transport input telnet
!
scheduler allocate 20000 1000
end

Switch (192.168.2.2) Config:

Current configuration : 3079 bytes
!
version 12.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname 3560-Lab
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
system mtu routing 1500
ip subnet-zero
!
!
!
!
!
!
!
!
spanning-tree mode pvst
spanning-tree etherchannel guard misconfig
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
!
!
interface FastEthernet0/1
description User Ports
switchport mode access
!
interface FastEthernet0/2
description User Ports
switchport mode access
!
interface FastEthernet0/3
description User Ports
switchport mode access
interface FastEthernet0/4
description User Ports
switchport mode access
!
interface FastEthernet0/5
description User Ports
switchport mode access
!
interface FastEthernet0/6
description User Ports
switchport mode access
!
interface FastEthernet0/7
description User Ports
switchport mode access
!
interface FastEthernet0/8
description User Ports
switchport mode access
!
interface FastEthernet0/9
description User Ports
switchport mode access
!
interface FastEthernet0/10
description User Ports
switchport mode access
!
interface FastEthernet0/11
description User Ports
switchport mode access
!
interface FastEthernet0/12
description User Ports
switchport mode access
!
interface FastEthernet0/13
description Lab Ports
switchport access vlan 2
switchport mode access
!
interface FastEthernet0/14
description Lab Ports
switchport access vlan 2
interface FastEthernet0/15
description Lab Ports
switchport access vlan 2
switchport mode access
!
interface FastEthernet0/16
description Lab Ports
switchport access vlan 2
switchport mode access
!
interface FastEthernet0/17
description Lab Ports
switchport access vlan 2
switchport mode access
!
interface FastEthernet0/18
description Lab Ports
switchport access vlan 2
switchport mode access
!
interface FastEthernet0/19
description Lab Ports
switchport access vlan 2
switchport mode access
!
interface FastEthernet0/20
description Lab Ports
switchport access vlan 2
switchport mode access
!
interface FastEthernet0/21
description Lab Ports
switchport access vlan 2
switchport mode access
!
interface FastEthernet0/22
description Lab Ports
switchport access vlan 2
switchport mode access
!
interface FastEthernet0/23
description Lab Ports
switchport access vlan 2
switchport mode access
!
interface FastEthernet0/24
description Uplink to Router Fa 0/1
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,2
switchport mode trunk
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
description User VLAN
ip address 192.168.1.2 255.255.255.0
!
interface Vlan2
description Lab VLAN
ip address 192.168.2.2 255.255.255.0
!
ip default-gateway 192.168.1.1
ip classless
ip http server
!
!
control-plane
!
!
line con 0
password temporary
logging synchronous
login
line vty 0 4
password temporary
login
transport input telnet
line vty 5 15
login
!
end

Message was edited by: kbreit

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Answer 7

Jul 31, 2009 3:59 AM in response to kbreit

Nothing obvious looks wrong to me. I will read over the config more thoroughly this weekend (I may even be able to try it out in my setup) and see if I can figure out what is happening.

Message was edited by: Noah Robbin

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Answer 8

Jul 31, 2009 5:08 AM in response to kbreit

Ok about Portfast, this suggestion may be a bit way out, I have never run 10.5.7 on Cisco switches ( I am not in a position to do any network testing now, it was 10.5.5 that I used) and 10.5.7 seems to have caused a lot of trouble for some users with their ethernet.
Is it worth trying an external drive with a clean 10.5.6 install?

Be interesting to see if Noah can replicate the problem.

best of luck

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Answer 9

Dogcow-Moof

Level 8

36,833 points

Jul 31, 2009 5:55 AM in response to kbreit

What is the order of interfaces in your Network preference pane?

Is the interface you're using the topmost interface, or are others (e.g. AirPort) above it?

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Answer 10

kbreit Author

Level 1

20 points

Jul 31, 2009 4:33 PM in response to Dogcow-Moof

Everyone - It hit me why it is broke a bit earlier today. Comcast binds your connection to the first MAC address it detects when the account is setup. In this case, it is my Mac. I cloned the Mac address (see the config) on my outside interface. This is why pinging the router doesn't work. There are duplicate MACs.

I am not 100% sure this is it because I haven't reconfigured, but it sounds pretty obvious to me at this point.

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Answer 11

direwolf8

Level 4

1,286 points

Jul 31, 2009 6:24 PM in response to kbreit

I didn't see any indication that you've set up VTP on the Cisco router and switch. If you're running trunked vlans, you usually need to set up VTP so the VLAN information is passed from the router to the switches.

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Answer 12

direwolf8

Level 4

1,286 points

Jul 31, 2009 6:26 PM in response to kbreit

I don't see how that would affect anything. You can't even reach a local address on the same Vlan. The router logging will tell you if it sees duplicate mac addresses, The one that you've manually set the address on isn't the inside interface you're trying to ping so shouldn't affect that.

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Answer 13

kbreit Author

Level 1

20 points

Aug 1, 2009 1:14 PM in response to direwolf8

@direwolf8: I can reach local addresses on the same VLAN. But as soon as it hits the router, pinging breaks. Here is why...the modified MAC address on the router is in a separate broadcast domain from the Mac/switch. When I ping my switch, it never hits the router. The switch has no knowledge of the cloned MAC address because it is in a separate broadcast domain. When I ping the router, this is where it falls apart. The router says "Oh, I gotta return this to MAC aa.bb.cc. Odd, I have that same MAC address too." Does that clarify?

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