Diagram 1
Lets start a about talking Bridging. Bridging is just like L2 switching. The purpose of Bridging is to make sure two or more hosts/devices on same IP Subnet should be able to communicate with each other without any problem. Which sounds similar to what SWITCHING does too. In short Bridging is a legacy way of doing the same stuff but using Routers rather than Switches.
There are many flavours of Bridging that can be achieved using routers. Some of them are meant to Switch/Bridge Non-IP Traffic between devices and some of them are meant to switch IP traffic among devices.
In this Bridging series we are going to discuss three common type of Bridging used to Bridge IP Traffic.
1. Transparent Bridging
2. CRB - Concurrent Routing and Bridging
3. IRB - Integrated Routing and Bridging
Lets start with Transparent Bridging and see how it works in different designs.
Transparent Bridging :
Transparent bridging forwards frames without modifying them. Transparent bridging takes multiple physical segments and combines them into what appears to the nodes to be a single data-link LAN. The transparent bridge has four distinct functions:
Learning
Forwarding
Filtering
Loop avoidance
Now lets hop on to Devices (Topology 1) and configure things out.
Here is the step by step configuration. In this topology R1 & R3 are acting as end host devices. Where R2 is working as a Bridge Device.
To Configure Bridge device in transparent bridging mode we need to disable "IP Routing" to make "router function as Layer 2 device".
In next step we need to enable Bridge Protocol IEEE with command " Bridge 1 protocol ieee". Where 1 is a random bridge group number.
In 3rd and last step we need to enable bridging on interfaces participating in bridging with command " bridge- group 1".
Keep in mind that when router work as a Bridge device all STP rules are applied to this layer 2 topology.
Now lets hop on to CLI to configure it:
!!! Transparent Bridging !!!
**********************
<<< R1 >>>
!
no ip routing <- To Disable IP Routing on Router to work as end host
!
interface FastEthernet0/0
ip address 13.13.13.1 255.255.255.0
no sh
!
#######################
<<< R3 >>>
!
no ip routing
!
interface FastEthernet0/0
ip address 13.13.13.3 255.255.255.0
no sh
!
#######################
<<< R2 >>> <- Bridge Device
!
no ip routing <- To Convert Router into a Layer 2 Bridge Device
!
bridge 1 protocol ieee <- To Enable Bridge Protocol IEEE to Bridge IP Traffic
!
interface FastEthernet0/0
no sh
bridge-group 1 <- To Enable Bridging under interfaces participating in Bridging
!
interface FastEthernet0/1
no sh
bridge-group 1
!
########################
Verification
*************************
R1(config)#do ping 13.13.13.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 13.13.13.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/45/108 ms
----------------------------
R3(config)#do ping 13.13.13.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 13.13.13.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/37/68 ms
----------------------------
R2#sh bridge 1 verbose
Total of 300 station blocks, 298 free
Codes: P - permanent, S - self
BG Hash Address Action Interface VC Age RX count TX count
1 00/0 c212.0908.0000 forward FastEthernet0/1 - 0 11 10
1 00/1 c210.0908.0000 forward FastEthernet0/0 - 0 3401 3398
Flood ports (BG 1) RX count TX count
FastEthernet0/0 2 3
FastEthernet0/1 3 2
-----------------------------
R2#sh spanning-tree 1
Bridge group 1 is executing the ieee compatible Spanning Tree protocol
Bridge Identifier has priority 32768, address c211.0908.0000
Configured hello time 2, max age 20, forward delay 15
We are the root of the spanning tree
Topology change flag not set, detected flag not set
Number of topology changes 2 last change occurred 00:18:52 ago
from FastEthernet0/1
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Timers: hello 1, topology change 0, notification 0, aging 300
Port 4 (FastEthernet0/0) of Bridge group 1 is forwarding
Port path cost 100, Port priority 128, Port Identifier 128.4.
Designated root has priority 32768, address c211.0908.0000
Designated bridge has priority 32768, address c211.0908.0000
Designated port id is 128.4, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 1
BPDU: sent 596, received 0
Port 5 (FastEthernet0/1) of Bridge group 1 is forwarding
Port path cost 100, Port priority 128, Port Identifier 128.5.
Designated root has priority 32768, address c211.0908.0000
Designated bridge has priority 32768, address c211.0908.0000
Designated port id is 128.5, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 1
BPDU: sent 581, received 0
*****************************
R4#ping 150.150.150.5 r 10
Type escape sequence to abort.
Sending 10, 100-byte ICMP Echos to 150.150.150.5, timeout is 2 seconds:
!!!!!!!!!!
Success rate is 100 percent (10/10), round-trip min/avg/max = 12/34/80 ms
R4#ping 150.150.150.6 r 10
Type escape sequence to abort.
Sending 10, 100-byte ICMP Echos to 150.150.150.6, timeout is 2 seconds:
!!!!!!!!!!
Success rate is 100 percent (10/10), round-trip min/avg/max = 12/32/116 ms
---------------------------
R5#ping 150.150.150.4 r 10
Type escape sequence to abort.
Sending 10, 100-byte ICMP Echos to 150.150.150.4, timeout is 2 seconds:
!!!!!!!!!!
Success rate is 100 percent (10/10), round-trip min/avg/max = 12/32/76 ms
R5#
R5#ping 150.150.150.6 r 10
Type escape sequence to abort.
Sending 10, 100-byte ICMP Echos to 150.150.150.6, timeout is 2 seconds:
!!!!!!!!!!
Success rate is 100 percent (10/10), round-trip min/avg/max = 16/40/128 ms
---------------------------
R6#ping 150.150.150.4 r 10
Type escape sequence to abort.
Sending 10, 100-byte ICMP Echos to 150.150.150.4, timeout is 2 seconds:
!!!!!!!!!!
Success rate is 100 percent (10/10), round-trip min/avg/max = 16/29/72 ms
R6#
R6#ping 150.150.150.5 r 10
Type escape sequence to abort.
Sending 10, 100-byte ICMP Echos to 150.150.150.5, timeout is 2 seconds:
!!!!!!!!!!
Success rate is 100 percent (10/10), round-trip min/avg/max = 16/45/192 ms
---------------------------
R1#sh bridge 1 verbose
Total of 300 station blocks, 295 free
Codes: P - permanent, S - self
BG Hash Address Action Interface VC Age RX count TX count
1 00/0 c21f.0d40.0000 forward FastEthernet0/0 - 3 1 0
1 00/1 c222.01d4.0000 forward FastEthernet0/0 - 0 91 90
1 00/2 c221.0d40.0000 forward FastEthernet1/0 - 0 77 76
1 00/3 c223.01d4.0000 forward FastEthernet0/1 - 0 102 95
1 3E/0 0000.0400.023c forward FastEthernet0/0 - 2 1 0
Flood ports (BG 1) RX count TX count
FastEthernet0/0 5 1
FastEthernet0/1 1 5
FastEthernet1/0 0 6
----------------------------
R2#sh bridge 1 verbose
Total of 300 station blocks, 295 free
Codes: P - permanent, S - self
BG Hash Address Action Interface VC Age RX count TX count
1 00/0 c21e.0d40.0000 forward FastEthernet0/0 - 2 1 0
1 00/1 c222.01d4.0000 forward FastEthernet1/0 - 1 92 89
1 00/2 c221.0d40.0000 forward FastEthernet0/0 - 2 42 41
1 00/3 c223.01d4.0000 forward FastEthernet0/0 - 1 60 55
1 3E/0 0000.0400.023c forward FastEthernet0/0 - 2 1 0
Flood ports (BG 1) RX count TX count
FastEthernet0/0 4 2
FastEthernet0/1 0 6
FastEthernet1/0 2 4
----------------------------
R3#sh bridge 1 verbose
Total of 300 station blocks, 294 free
Codes: P - permanent, S - self
BG Hash Address Action Interface VC Age RX count TX count
1 00/0 c21f.0d40.0000 forward FastEthernet0/0 - 4 1 0
1 00/1 c221.0d40.0000 forward FastEthernet0/0 - 1 36 35
1 00/2 c223.01d4.0000 forward FastEthernet1/0 - 1 102 95
1 00/3 c222.01d4.0000 forward FastEthernet0/0 - 1 61 56
1 01/0 c21e.0d40.0001 forward FastEthernet0/0 - 2 1 0
1 3E/0 0000.0400.023c forward FastEthernet0/0 - 2 3 0
Flood ports (BG 1) RX count TX count
FastEthernet0/0 11 1
FastEthernet0/1 0 0
FastEthernet1/0 1 11
----------------------------
R1#sh span br
Bridge group 1
Spanning tree enabled protocol ieee
Root ID Priority 32768
Address c21e.0d40.0000
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768
Address c21e.0d40.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Designated
Name Port ID Prio Cost Sts Cost Bridge ID Port ID
-------------------- ------- ---- ----- --- ----- -------------------- -------
FastEthernet0/0 128.4 128 100 FWD 0 32768 c21e.0d40.0000 128.4
FastEthernet0/1 128.5 128 100 FWD 0 32768 c21e.0d40.0000 128.5
FastEthernet1/0 128.6 128 19 FWD 0 32768 c21e.0d40.0000 128.6
---------------------------
R2#sh span br
Bridge group 1
Spanning tree enabled protocol ieee
Root ID Priority 32768
Address c21e.0d40.0000
Cost 100
Port 4 (FastEthernet0/0)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768
Address c21f.0d40.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Designated
Name Port ID Prio Cost Sts Cost Bridge ID Port ID
-------------------- ------- ---- ----- --- ----- -------------------- -------
FastEthernet0/0 128.4 128 100 FWD 0 32768 c21e.0d40.0000 128.4
FastEthernet0/1 128.5 128 100 FWD 100 32768 c21f.0d40.0000 128.5
FastEthernet1/0 128.6 128 19 FWD 100 32768 c21f.0d40.0000 128.6
----------------------------
R3#sh span brief
Bridge group 1
Spanning tree enabled protocol ieee
Root ID Priority 32768
Address c21e.0d40.0000
Cost 100
Port 4 (FastEthernet0/0)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768
Address c220.0d40.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Designated
Name Port ID Prio Cost Sts Cost Bridge ID Port ID
-------------------- ------- ---- ----- --- ----- -------------------- -------
FastEthernet0/0 128.4 128 100 FWD 0 32768 c21e.0d40.0000 128.5
FastEthernet0/1 128.5 128 100 BLK 100 32768 c21f.0d40.0000 128.5
FastEthernet1/0 128.6 128 19 FWD 100 32768 c220.0d40.0000 128.6
------------------------------
R1#sh span root
Bridge group 1
Root ID Priority 32768
Address c21e.0d40.0000
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
------------------------------
R2#sh span root
Bridge group 1
Root ID Priority 32768
Address c21e.0d40.0000
Cost 100
Port 4 (FastEthernet0/0)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
------------------------------
R3#sh span root
Bridge group 1
Root ID Priority 32768
Address c21e.0d40.0000
Cost 100
Port 4 (FastEthernet0/0)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
###############################
R1#sh span block
Name Blocked Interfaces List
-------------------- ------------------------------------
Number of blocked ports (segments) in the system : 0
###############################
R2#sh span block
Name Blocked Interfaces List
-------------------- ------------------------------------
Number of blocked ports (segments) in the system : 0
###############################
R3#sh span block
Name Blocked Interfaces List
-------------------- ------------------------------------
Bridge group 1 Fa0/1
Number of blocked ports (segments) in the system : 1
###############################
R1#sh vlan-switch
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup
VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
1 enet 100001 1500 - - - - - 1002 1003
1002 fddi 101002 1500 - - - - - 1 1003
1003 tr 101003 1500 1005 0 - - srb 1 1002
1004 fdnet 101004 1500 - - 1 ibm - 0 0
1005 trnet 101005 1500 - - 1 ibm - 0 0
###############################
R3(config)#spanning-tree vlan 1 root primary
VLAN 1 bridge priority set to 8192
VLAN 1 bridge max aging time unchanged at 20
VLAN 1 bridge hello time unchanged at 2
VLAN 1 bridge forward delay unchanged at 15
###############################
R3(config)#spanning-tree vlan 1 p
R3(config)#do sh span root
Bridge group 1
Root ID Priority 32768
Address c21e.0d40.0000
Cost 100
Port 4 (FastEthernet0/0)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
###############################
R3(config)#spanning-tree vlan 1 priority 0
R3(config)#
R3(config)#do sh span root
Bridge group 1
Root ID Priority 32768
Address c21e.0d40.0000
Cost 100
Port 4 (FastEthernet0/0)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
##############################
R3(config)#bridge 1 priority 0
R3(config)#
R3(config)#do sh span root
Bridge group 1
Root ID Priority 0
Address c220.0d40.0000
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
#############################
R3(config)#do sh span block
Name Blocked Interfaces List
-------------------- ------------------------------------
Number of blocked ports (segments) in the system : 0
#############################
R2#sh span block
Name Blocked Interfaces List
-------------------- ------------------------------------
Bridge group 1 Fa0/0
Number of blocked ports (segments) in the system : 1
<<< R1 >>>
!
no ip routing
!
bridge 1 protocol ieee
!
interface FastEthernet0/0
no ip address
bridge-group 1
no sh
!
interface FastEthernet0/1
no ip address
bridge-group 1
no sh
!
interface FastEthernet1/0
no ip address
bridge-group 1
no sh
!
==========================
<<< R2 >>>
!
no ip routing
!
bridge 1 protocol ieee
!
interface FastEthernet0/0
no ip address
bridge-group 1
no sh
!
interface FastEthernet0/1
no ip address
bridge-group 1
no sh
!
interface FastEthernet1/0
no ip address
bridge-group 1
no sh
!
interface FastEthernet2/0
no ip address
bridge-group 1
no sh
!
=============================
<<< R3 >>>
!
no ip routing
!
bridge 1 protocol ieee
!
interface FastEthernet0/0
no ip address
bridge-group 1
no sh
!
interface FastEthernet0/1
no ip address
bridge-group 1
no sh
!
interface FastEthernet1/0
no ip address
bridge-group 1
no sh
!
==============================
<<< R4 >>>
!
no ip routing
!
interface FastEthernet0/0
ip address 45.45.45.4 255.255.255.0
no sh
!
==============================
<<< R5 >>>
!
no ip routing
!
interface FastEthernet0/0
ip address 45.45.45.5 255.255.255.0
no sh
!
==============================
*******************************
R5#ping 45.45.45.4 si 1500 r 3
Type escape sequence to abort.
Sending 3, 1500-byte ICMP Echos to 45.45.45.4, timeout is 2 seconds:
!!!
Success rate is 100 percent (3/3), round-trip min/avg/max = 64/88/128 ms
*******************************
R4#ping 45.45.45.5 si 1500 r 3
Type escape sequence to abort.
Sending 3, 1500-byte ICMP Echos to 45.45.45.5, timeout is 2 seconds:
!!!
Success rate is 100 percent (3/3), round-trip min/avg/max = 40/109/208 ms
R4#
********************************
R2#sh br 1 v
Total of 300 station blocks, 294 free
Codes: P - permanent, S - self
BG Hash Address Action Interface VC Age RX count TX count
1 00/0 c21b.0a14.0000 forward FastEthernet0/0 - 0 10 8
1 00/1 c21a.0a14.0000 forward FastEthernet1/0 - 3 1 0
1 00/2 c21c.0c84.0000 forward FastEthernet1/0 - 0 9 8
1 01/0 0025.0000.0001 forward FastEthernet0/0 - 2 1 0
1 01/1 c21a.0a14.0001 forward FastEthernet2/0 - 3 1 0
1 3E/0 0000.0400.023c forward FastEthernet0/0 - 3 4 0
Flood ports (BG 1) RX count TX count
FastEthernet0/0 19 11
FastEthernet0/1 0 0
FastEthernet1/0 7 23
FastEthernet2/0 4 26
---------------------------------
R2#sh span br
Bridge group 1
Spanning tree enabled protocol ieee
Root ID Priority 32768
Address c218.0a14.0000
Cost 19
Port 4 (FastEthernet0/0)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768
Address c219.0a14.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Designated
Name Port ID Prio Cost Sts Cost Bridge ID Port ID
-------------------- ------- ---- ----- --- ----- -------------------- -------
FastEthernet0/0 128.4 128 19 FWD 0 32768 c218.0a14.0000 128.4
FastEthernet0/1 128.5 128 19 BLK 0 32768 c218.0a14.0000 128.5
FastEthernet1/0 128.6 128 19 FWD 19 32768 c219.0a14.0000 128.6
FastEthernet2/0 128.7 128 19 FWD 19 32768 c219.0a14.0000 128.7
**********************************
R1#sh br 1 v
Total of 300 station blocks, 293 free
Codes: P - permanent, S - self
BG Hash Address Action Interface VC Age RX count TX count
1 00/0 c219.0a14.0000 forward FastEthernet0/0 - 0 1 0
1 00/1 c21b.0a14.0000 forward FastEthernet1/0 - 1 13 8
1 00/2 c21a.0a14.0000 forward FastEthernet0/0 - 4 1 0
1 00/3 c21c.0c84.0000 forward FastEthernet0/0 - 1 9 9
1 01/0 c219.0a14.0001 forward FastEthernet0/1 - 0 1 0
1 01/1 c21a.0a14.0001 forward FastEthernet0/0 - 4 1 0
1 3E/0 0000.0400.023c forward FastEthernet0/0 - 1 3 0
Flood ports (BG 1) RX count TX count
FastEthernet0/0 18 11
FastEthernet0/1 4 25
FastEthernet1/0 7 22
-------------------------------------
R1#sh span br
Bridge group 1
Spanning tree enabled protocol ieee
Root ID Priority 32768
Address c218.0a14.0000
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768
Address c218.0a14.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Designated
Name Port ID Prio Cost Sts Cost Bridge ID Port ID
-------------------- ------- ---- ----- --- ----- -------------------- -------
FastEthernet0/0 128.4 128 19 FWD 0 32768 c218.0a14.0000 128.4
FastEthernet0/1 128.5 128 19 FWD 0 32768 c218.0a14.0000 128.5
FastEthernet1/0 128.6 128 19 FWD 0 32768 c218.0a14.0000 128.6
***************************************
R3#sh br 1 v
Total of 300 station blocks, 294 free
Codes: P - permanent, S - self
BG Hash Address Action Interface VC Age RX count TX count
1 00/0 c218.0a14.0000 forward FastEthernet0/0 - 1 1 0
1 00/1 c21b.0a14.0000 forward FastEthernet0/0 - 0 11 9
1 00/2 c21c.0c84.0000 forward FastEthernet1/0 - 0 10 9
1 01/0 0025.0000.0001 forward FastEthernet0/0 - 2 3 0
1 10/0 c219.0a14.0010 forward FastEthernet0/0 - 2 1 0
1 3E/0 0000.0400.023c forward FastEthernet0/0 - 2 5 0
Flood ports (BG 1) RX count TX count
FastEthernet0/0 29 3
FastEthernet0/1 0 0
FastEthernet1/0 3 29
---------------------------------------
R3#sh span br
Bridge group 1
Spanning tree enabled protocol ieee
Root ID Priority 32768
Address c218.0a14.0000
Cost 38
Port 4 (FastEthernet0/0)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768
Address c21a.0a14.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Designated
Name Port ID Prio Cost Sts Cost Bridge ID Port ID
-------------------- ------- ---- ----- --- ----- -------------------- -------
FastEthernet0/0 128.4 128 19 FWD 19 32768 c219.0a14.0000 128.6
FastEthernet0/1 128.5 128 19 BLK 19 32768 c219.0a14.0000 128.7
FastEthernet1/0 128.6 128 19 FWD 38 32768 c21a.0a14.0000 128.6
*****************************************
R1#sh span root
Bridge group 1
Root ID Priority 32768
Address c218.0a14.0000
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
#########################################
R2#sh span root
Bridge group 1
Root ID Priority 32768
Address c218.0a14.0000
Cost 19
Port 4 (FastEthernet0/0)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
#########################################
R3#sh span root
Bridge group 1
Root ID Priority 32768
Address c218.0a14.0000
Cost 38
Port 4 (FastEthernet0/0)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
#########################################
!!! Transparent Bridging With Multiple-Links !!!
**********************
<<< R1 >>>
!
no ip routing
!
interface FastEthernet0/0
ip address 13.13.13.1 255.255.255.0
no sh
!
#######################
<<< R3 >>>
!
no ip routing
!
interface FastEthernet0/0
ip address 13.13.13.3 255.255.255.0
no sh
!
#######################
<<< R2 >>>
!
no ip routing
!
bridge 1 protocol ieee
!
interface FastEthernet0/0
no ip address
bridge-group 1
no sh
!
interface FastEthernet0/1
no ip address
bridge-group 1
no sh
!
interface FastEthernet1/0
no ip address
bridge-group 1
no sh
!
interface FastEthernet2/0
no ip address
bridge-group 1
no sh
!
########################
*************************
R1(config)#do ping 13.13.13.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 13.13.13.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/45/108 ms
----------------------------
R3(config)#do ping 13.13.13.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 13.13.13.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/37/68 ms
----------------------------
R2#sh bridge 1 verbose
Total of 300 station blocks, 298 free
Codes: P - permanent, S - self
BG Hash Address Action Interface VC Age RX count TX count
1 00/0 c214.0de0.0000 forward FastEthernet0/0 - 0 5 4
1 00/1 c216.0de0.0000 forward FastEthernet1/0 - 0 5 5
Flood ports (BG 1) RX count TX count
FastEthernet0/0 2 3
FastEthernet0/1 0 0
FastEthernet1/0 3 2
FastEthernet2/0 0 0
-----------------------------
R2#sh span brief
Bridge group 1
Spanning tree enabled protocol ieee
Root ID Priority 32768
Address c215.0de0.0000
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768
Address c215.0de0.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Designated
Name Port ID Prio Cost Sts Cost Bridge ID Port ID
-------------------- ------- ---- ----- --- ----- -------------------- -------
FastEthernet0/0 128.4 128 100 FWD 0 32768 c215.0de0.0000 128.4
FastEthernet0/1 128.5 128 100 BLK 0 32768 c215.0de0.0000 128.4
FastEthernet1/0 128.6 128 19 FWD 0 32768 c215.0de0.0000 128.6
FastEthernet2/0 128.7 128 19 BLK 0 32768 c215.0de0.0000 128.6
*****************************
