& Switching v5 Workbook -
Advanced Technology Labs - IP
CCIE Routing
CCIE R&S v5
Routing
Reliable Static Routing with Enhanced Object Tracking
A Note On Section Initial Configuration Files: You must load the
initial configuration files for the section, named Basic IP Addressing,
which can be found in
. Reference the Advanced Technology Labs With
Addressing Diagram to complete this task.
Task
Configure R1 with IPv4 static route for R4’s Loopback0 prefix through the DMVPN
cloud.
Configure R5 with IPv4 static routes for R1’s and R4’s Loopback0 prefixes through
the DMVPN cloud.
Configure R4 with a primary IPv4 static route for R1’s Loopback0 prefix via its
VLAN146 Ethernet connection.
use SLA and Object Tracking to ensure the route is valid as long as ICMP
connectivity exists between R1 and R4’s Ethernet connection.
configure R4 to verify connectivity each 5 seconds.
ensure R1 replies within 2 seconds.
Configure R4 with a backup IPv4 static route for R1’s Loopback0 prefix through the
DMVPN cloud using administrative distance of 2.
Configuration
R1:
ip route 150.1.4.4 255.255.255.255 155.1.0.4
R4:
ip sla 1
icmp-echo 155.1.146.1 source-interface GigabitEthernet1.146
threshold 2000
timeout 2000
frequency 5
ip sla schedule 1 life forever start-time now
!
track 1 ip sla 1 state
!
ip route 150.1.1.1 255.255.255.255 155.1.146.1 track 1
ip route 150.1.1.1 255.255.255.255 155.1.0.1 2
R5:
ip route 150.1.1.1 255.255.255.255 155.1.0.1
ip route 150.1.4.4 255.255.255.255 155.1.0.4
Verification
Although R1 and R4 are on the same Layer 2 segment in VLAN 146, their physical
Ethernet interfaces are not on the same Layer 1 network; there is no back-to-back
Ethernet cable between the two routers, connectivity is achieved through a
switching infrastructure. This means that the Layer 1 link status of R1’s connection
to VLAN 146 is independent of R4’s Layer 1 link status, and vice-versa. From a
static routing redundancy design point of view, the possible problem with this
scenario is that routers have no way of detecting the other peer link failure, which
may result in traffic being blackholed and silently dropped in the transit path.
To visualize this, before implementing the tracking functionality for the static route
let’s shutdown R1’s Ethernet interface, which will still keep the primary route in the
routing table, however IPv4 connectivity will fail:
R1#ping 150.1.4.4 source 150.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 150.1.4.4, timeout is 2 seconds:
Packet sent with a source address of 150.1.1.1 !!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 56/58/60 ms
!R1(config)#interface gigabitEthernet1.146
R1(config-subif)#shutdown
!R4#show ip route 150.1.1.1
Routing entry for150.1.1.1/32
Known via "static", distance 1, metric 0
Routing Descriptor Blocks: *155.1.146.1
Route metric is 0, traffic share count is 1
!R1#ping 150.1.4.4 source 150.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 150.1.4.4, timeout is 2 seconds:
Packet sent with a source address of 150.1.1.1 .....
To fix the problem, we need to actively monitor IPv4 connectivity between R1 and
R4 on the Ethernet segment and mark the primary static route as invalid for being
installed in the routing table when connectivity fails. For this scope, IP Service Level
Agreement (SLA) and Enhanced Object Tracking features is used. First, R4 is
configured with a SLA instance that actively monitors IPv4 connnectivity with R1
over the Ethernet link by sending ICMP Echo Request packets each 5 seconds.
SLA will consider connectivity to be functional through the Return Code of OK as
long as ICMP Echo Reply is received within the configured 2 seconds timeout
window; otherwise the Return Code will be Timeout:
R4#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.R4(config)#ip sla 1
R4(config-sla-monitor)#icmp-echo 155.1.146.1 source-interface GigabitEthernet1.146
R4(config-sla-monitor-echo)#frequency 5
R4(config-sla-monitor-echo)#timeout 2000
R4(config-sla-monitor-echo)#exit
R4(config)#ip sla schedule 1 life forever start-time now
!R4#show ip sla configuration 1
IP SLAs Infrastructure Engine-III
Entry number: 1
Owner:
Tag: Operation timeout (milliseconds): 2000
Type of operation to perform: icmp-echo
Target address/Source interface: 155.1.146.1/GigabitEthernet1.146
Type Of Service parameter: 0x0
Request size (ARR data portion): 28
Verify data: No
Vrf Name:
Schedule:Operation frequency (seconds): 5 (not considered if randomly scheduled)
Next Scheduled Start Time: Start Time already passed
Group Scheduled : FALSE
Randomly Scheduled : FALSE
Life (seconds): Forever
Entry Ageout (seconds): never
Recurring (Starting Everyday): FALSE
Status of entry (SNMP RowStatus): Active
Threshold (milliseconds): 2000
Distribution Statistics:
Number of statistic hours kept: 2
Number of statistic distribution buckets kept: 1
Statistic distribution interval (milliseconds): 20
Enhanced History:
History Statistics:
Number of history Lives kept: 0
Number of history Buckets kept: 15
History Filter Type: None
!R4#show ip sla statistics
IPSLAs Latest Operation Statistics
IPSLA operation id: 1
Latest RTT: 1 milliseconds
Latest operation start time: 15:59:53 UTC Sat May 3 2014Latest operation return code: OK
Number of successes: 2
Number of failures: 0
Operation time to live: Forever
Next, a Enhanced Object Tracking is created that monitors the IP SLA instance
Return Code. If SLA Return Code is OK, the tracking state is UP, while if the SLA
Return Code has any other value, the tracking state is DOWN:
R4#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.R4(config)#track 1 ip sla 1 state
!R4#show track
Track 1IP SLA 1 state
State is Up
2 changes, last change 00:00:26
Latest operation return code: OK
Latest RTT (millisecs) 2
Next the primary static route is configured with the tracking object attached as a
condition. This will instruct the router to consider the route as valid for being entered
in the routing table as long as the tracking state is UP. Also note that tracking now
shows it is attached to static routing:
R4(config)#ip route 150.1.1.1 255.255.255.255 155.1.146.1 track 1
!R4#show track
Track 1
IP SLA 1 state
State is Up
2 changes, last change 00:02:02
Latest operation return code: OK
Latest RTT (millisecs) 1
Tracked by:Static IP Routing 0
!R4#show ip route static | b Gateway
Gateway of last resort is not set
150.1.0.0/32 is subnetted, 1 subnetsS150.1.1.1 [1/0] via 155.1.146.1
We simulate the same network failure, however due to tracking being configured for
the primary route, once R4 will detect loss of IPv4 connectivity with R1, it will mark
the primary route as invalid and inject the backup route in the routing table:
R4#traceroute 150.1.1.1 source 150.1.4.4
Type escape sequence to abort.
Tracing the route to 150.1.1.1
1 155.1.146.1 36 msec * 36 msec
!R4#debug track state
track state debugging enabled
!R4#debug ip routing
IP routing debugging is on
!R1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.R1(config)#interface gigabitEthernet1.146
R1(config-subif)#shutdown
!R4#
Track: 1 Change #3 rtr 1, state Up->Down
%TRACK-6-STATE: 1 ip sla 1 state Up -> Downtrack-sta (1) ip sla 1 state Up -> Down
RT: del 150.1.1.1 via 155.1.146.1, static metric [1/0]RT: delete subnet route to 150.1.1.1/32
RT: updating static 150.1.1.1/32 (0x0) :
via 155.1.0.1 0 1048578
RT: add 150.1.1.1/32 via 155.1.0.1, static metric [2/0]
RT: updating static 150.1.1.1/32 (0x0) :
via 155.1.0.1 0 1048578
!R4#traceroute 150.1.1.1 source 150.1.4.4
Type escape sequence to abort.
Tracing the route to 150.1.1.1
1 155.1.0.5 28 msec 28 msec 28 msec
2 155.1.0.1 56 msec * 56 msec
!R4#show ip route 150.1.1.1
Routing entry for150.1.1.1/32
Known via "static", distance 2, metric 0
Routing Descriptor Blocks: *155.1.0.1
Route metric is 0, traffic share count is 1
Verify the SLA and tracking states:
R4#show ip sla statistics 1
IPSLAs Latest Operation Statistics
IPSLA operation id: 1
Latest RTT: NoConnection/Busy/Timeout
Latest operation start time: 16:36:54 UTC Sat May 3 2014Latest operation return code: Timeout
Number of successes: 82
Number of failures: 70
Operation time to live: Forever
!R4#show track
Track 1
IP SLA 1 stateState is Down
3 changes, last change 00:05:39Latest operation return code: Timeout
Tracked by:
Static IP Routing 0
When we re-activate R1’s VLAN 146 Ethernet connection, the SLA instance reports
itself as back up, the tracking instance reports itself as back up, and the static route
with the lower administrative distance is re-installed in the routing table:
R1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.R1(config)#interface gigabitEthernet1.146
R1(config-if)#no shutdown
!
!R4#
track-sta (1) Change #4 ip sla 1, state Down->Up
%TRACK-6-STATE: 1 ip sla 1 state Down -> Uptrack-sta (1) ip sla 1 state Down -> Up
RT: updating static 150.1.1.1/32 (0x0) :
via 155.1.0.1 0 1048578
RT: updating static 150.1.1.1/32 (0x0) :
via 155.1.146.1 0 1048578
RT: closer admin distance for 150.1.1.1, flushing 1 routes
RT: add 150.1.1.1/32 via 155.1.146.1, static metric [1/0]
RT: updating static 150.1.1.1/32 (0x0) :
via 155.1.0.1 0 1048578
RT: rib update return code: 17
!R4#traceroute 150.1.1.1 source 150.1.4.4
Type escape sequence to abort.
Tracing the route to 150.1.1.1
1 155.1.146.1 40 msec * 36 msec