- We use a higher admin distance to create backup routes the thinking behind it is that the primary route will be selected by using a lower admin distance when recursion fails for a route if there is failure in connectivity it is taken out of the routing able and the next best admin distance will take over
- by default statics have admin distance of 1
- We could use this for 2 statics are maybe dynamic primary and static floating.
ip route "destination" " mask" " admin distance"
LAB
int this lab i used r4 and r5. r5 will have loopback configured of 6.6.6.6. I will
create 2 static routes on r4 to this address. The primary path will be through the
frame-relay interface on r4 the backup path will be through a directly connected
serial connection
so r4 s0/0/0 frame-relay with Next hop 10.229.254.2 primary path
r4 backup will s0/1/0 with next hop 172.25.14.2
i confirmed connectivity before doing anything
r4(config)#IP ROUTE 6.6.6.6 255.255.255.255 10.229.254.2
r4(config)#IP ROUTE 6.6.6.6 255.255.255.255 172.25.14.2 30
r4(config)#
r4(config)#do sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
6.0.0.0/32 is subnetted, 1 subnets
S 6.6.6.6 [1/0] via 10.229.254.2
172.25.0.0/24 is subnetted, 1 subnets
C 172.25.14.0 is directly connected, Serial0/1/0
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.229.254.0/24 is directly connected, Serial0/0/0
so now in the routing table we only have the route to the next hop of 10.229.254.2
and ping success
r4#ping 6.6.6.6
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 6.6.6.6, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/65/68 ms
r4#
On r5 i will shut the interface s0/0/0 which is 10.229.254.2
r5#config t
Enter configuration commands, one per line. End with CNTL/Z.
r5(config)#int s0/0/0
r5(config-if)#shut
r5(config-if)#exit
r5(config)#exit
on r4 the route is still via 10.229.254.2
r4#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
6.0.0.0/32 is subnetted, 1 subnets
S 6.6.6.6 [1/0] via 10.229.254.2
172.25.0.0/24 is subnetted, 1 subnets
C 172.25.14.0 is directly connected, Serial0/1/0
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
S 10.0.0.0/8 [1/0] via 10.229.254.1
C 10.229.254.0/24 is directly connected, Serial0/0/0
r4#ping 6.6.6.6
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 6.6.6.6, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
but not pinging
This shows the limitation of this the problem is because this is a multipoint
interface and there is intermediatry device the frame-relay switch even if the
circuit is down
r4#sh frame-relay pvc 405
PVC Statistics for interface Serial0/0/0 (Frame Relay DTE)
DLCI = 405, DLCI USAGE = LOCAL, PVC STATUS = INACTIVE, INTERFACE = Serial0/0/0
input pkts 42 output pkts 39 in bytes 8989
out bytes 9567 dropped pkts 0 in pkts dropped 0
out pkts dropped 0 out bytes dropped 0
in FECN pkts 0 in BECN pkts 0 out FECN pkts 0
out BECN pkts 0 in DE pkts 0 out DE pkts 0
out bcast pkts 29 out bcast bytes 8527
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
pvc create time 00:38:09, last time pvc status changed 00:04:49
the serial interface will remain up as it is a multipoint and could be servicing
other pvc
r4#sh ip int s0/0/0
Serial0/0/0 is up, line protocol is up
Internet address is 10.229.254.1/24
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 disabled
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 disabled
IP CEF switching is enabled
IP CEF Fast switching turbo vector
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
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
if i go to the s0/0/0 on r4 and do
r4(config-if)#frame-relay lmi-type ansi
this will bring down all circuits and s0/0/0 will go down
r4#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
6.0.0.0/32 is subnetted, 1 subnets
S 6.6.6.6 [30/0] via 172.25.14.2
172.25.0.0/24 is subnetted, 1 subnets
C 172.25.14.0 is directly connected, Serial0/1/0
no the route via s0/1 looks attractive and put in the routing table
r4#ping 6.6.6.6
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 6.6.6.6, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
r4#
This behaviour is dependent on the interface type you use it next example of backup
interface which work on the same logic of floating static route looking at the line
interface i will use frame-relay point-to-point interface
Backup Interface
- 2 static pointing at different interfaces one with larger admin distance
- you set the interface with the lower admin static asprimary
- the other interface secondary.
Commands
!
interface Serial0/0/0.1 point-to-point
backup interface Serial0/1/0
ip address 10.229.254.1 255.255.255.0
frame-relay interface-dlci 405
end
ip route 6.6.6.6 255.255.255.255 10.229.254.2
ip route 6.6.6.6 255.255.255.255 172.25.14.2
adding the routes
r4#sh ip i
*Dec 9 21:46:38.983: %SYS-5-CONFIG_I: Configured from console by consolent brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES NVRAM administratively down down
FastEthernet0/1 unassigned YES NVRAM administratively down down
Serial0/0/0 unassigned YES TFTP up up
Serial0/0/0.1 10.229.254.1 YES manual up up
Serial0/1/0 172.25.14.1 YES manual standby mode down
r4#ping 6.6.6.6
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 6.6.6.6, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5),
notice serial0/1/1 is in standby mode
in the routing table you notice there is only the one route to 6.6.6.6 even though
they were configured with the same admin distance as s0/1/0 is in standby mode and
down recursion fails and route is not installed
r4#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
6.0.0.0/32 is subnetted, 1 subnets
S 6.6.6.6 [1/0] via 10.229.254.2
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
S 10.0.0.0/8 [1/0] via 10.229.254.1
C 10.229.254.0/24 is directly connected, Ser
r5(config)#int s0/0/0
r5(config-if)#shut
r5(config-if)#exit
r5(config)#exit
r5#
*Dec 9 22:01:29.251: %LINK-5-CHANGED: Interface Serial0/0/0, changed state to
administratively down
*Dec 9 22:01:29.451: %SYS-5-CONFIG_I: Configured from console by console
*Dec 9 22:01:30.251: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0/0,
changed state to down
r5#
access#sh sess
Conn Host Address Byte Idle Conn Name
1 fr 90.90.90.90 221 01:05 fr
* 2 r5 90.90.90.90 0 0 r5
3 r1 90.90.90.90 237 37 r1
4 r4 90.90.90.90 0 0 r4
access#4
[Resuming connection 4 to r4 ... ]
*Dec 9 21:47:54.863: %LINK-3-UPDOWN: Interface Serial0/1/0, changed state to up
*Dec 9 21:47:55.863: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/1/0,
changed state to up
I shutdown r5 int s0/0/0 and on r4 s0/1/0 has become up up
r4#sh ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES NVRAM administratively down down
FastEthernet0/1 unassigned YES NVRAM administratively down down
Serial0/0/0 unassigned YES TFTP up up
Serial0/0/0.1 10.229.254.1 YES manual down down
Serial0/1/0 172.25.14.1 YES manual up up
i done a no shut on the s0/0/0 on r5
and on r4 the primary preemptied the backup
r4#sh ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES NVRAM administratively down down
FastEthernet0/1 unassigned YES NVRAM administratively down down
Serial0/0/0 unassigned YES TFTP up up
Serial0/0/0.1 10.229.254.1 YES manual up up
Serial0/1/0 172.25.14.1 YES manual standby mode down
r4#
*Dec 9 21:51:14.875: %LINK-5-CHANGED: Interface Serial0/1/0, changed state to
standby mode
*Dec 9 21:51:15.875: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/1/0,
changed state to down
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