Friday, December 9, 2011

FLOATING STATICS AND BACKUP INTERFACE

Floating Static Routes
  • 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.
Commands

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.
ok so on r4 i will create point-to-point interface s0/0/0,1

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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