At 12:17 AM 6/22/02, Tim Potier wrote:
>Lets say I have HSRP configured on a series of routers... I know clients are
>sending packets to the MAC/IP of the well known "virtual MAC" with Cisco
>equipment. Assume the receiving station recieves the packet directly from
>the router participating in HSRP with the highest priority... what is the
>source MAC the receiving station sees?
The reply will come from the actual MAC address of the router interface. At
this point, the router is just forwarding packets. It doesn't care that
HSRP is configured. I tried a test. I have 2 routers (Albany and Charlotte)
and a PC, like this:
more nets more nets
| |
| |
Albany--------------Ethernet------------Charlotte
10.10.0.1 | 10.10.0.2
00 00 0C 05 3E 80 | 00 00 0C 00 2E 75
standby ip 10.0.0.3 | standby ip 10.0.0.3
|
|
PC
address = 10.10.0.10
gateway = 10.10.0.3
running EtherPeek
Albany#show standby
Ethernet0 - Group 0
Local state is Active, priority 100
Hellotime 3 holdtime 10
Next hello sent in 0:00:02
Hot standby IP address is 10.10.0.3 configured
Active router is local
Standby router is 10.10.0.2 expires in 0:00:09
charlotte#show standby
Ethernet0 - Group 0
Local state is Standby, priority 100
Hellotime 3 holdtime 10
Next hello sent in 0:00:00
Hot standby IP address is 10.0.0.3 configured
Active router is 10.10.0.1 expires in 0:00:07
Standby router is local
charlotte#
Albany is active. The MAC virtual address is 00:00:0C:07:AC:00.
I ping to anything on the network from my PC. If the destination is
reachable via Charlotte, then I see the packet go from my PC MAC to
00:00:0C:07:AC:00 (the virtual MAC address.) Then I see the same packet go
from Albany's real MAC address to Charlotte's real MAC address (with no
ICMP Redirect, by the way).
If the destination is reachable via Albany, then I don't see the second
packet.
Regardless, in all cases the ping reply comes back from the real MAC
address of Albany or Charlotte.
Here's the simpler case where I pinged 172.16.50.1 which is reachable via
Albany. Ping:
Ethernet Header
Destination: 00:00:0C:07:AC:00
Source: 00:00:0E:D5:C7:E7
Protocol Type: 0x0800 IP
IP Header - Internet Protocol Datagram
Version: 4
Header Length: 5 (20 bytes)
Type of Service: %00000000
Total Length: 60
Identifier: 6400
Fragmentation Flags: %000
Fragment Offset: 0 (0 bytes)
Time To Live: 32
Protocol: 1 ICMP - Internet Control Message Protocol
Header Checksum: 0x999C
Source IP Address: 10.10.0.10
Dest. IP Address: 172.16.50.1
No IP Options
ICMP - Internet Control Messages Protocol
ICMP Type: 8 Echo Request
Code: 0
Checksum: 0x355C
Identifier: 0x0200
Sequence Number: 0x0016
Ping Reply:
Ethernet Header
Destination: 00:00:0E:D5:C7:E7
Source: 00:00:0C:05:3E:80
Protocol Type: 0x0800 IP
IP Header - Internet Protocol Datagram
Version: 4
Header Length: 5 (20 bytes)
Type of Service: %00000000
Total Length: 60
Identifier: 6400
Fragmentation Flags: %000
Fragment Offset: 0 (0 bytes)
Time To Live: 255
Protocol: 1 ICMP - Internet Control Message Protocol
Header Checksum: 0xBA9B
Source IP Address: 172.16.50.1
Dest. IP Address: 10.10.0.10
No IP Options
ICMP - Internet Control Messages Protocol
ICMP Type: 0 Echo Reply
Code: 0
Checksum: 0x3D5C
Identifier: 0x0200
Sequence Number: 0x0016
HTH.
Priscilla
________________________
Priscilla Oppenheimer
http://www.priscilla.com
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=47212&t=47177
--------------------------------------------------
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
