INE R&S ATC036 - On-Demand Routing (ODR)

On Demand Routing

• Uses CDP to advertise directly connected networks to “hub” router
– Hub router advertises default route to “stub” router via CDP
– No routing protocols allowed on stub router

• Configuration on Hub
– router odr


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R5當成 Hub, 啟動 router odr
    因為R5使用 Main Multipoint Frame-Relay interface...預設cdp disable...要下cdp enable開啟

其他路由器 - 使用Frame-Relay Subinterface...預設cdp enable

Hub 會收到 stub 路由器所有direct connection介面的路由...代號為 o , AD值預設為 160

Stub 會收到一筆 default gateway的路由...代號為 o , AD值預設為 160

以下為網路上 copy 來的 stub2 範例...

Stub2# show ip route
Codes: L - local, 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, + - replicated route

Gateway of last resort is 10.0.2.1 to network 0.0.0.0

o*    0.0.0.0/0 [160/1] via 10.0.2.1, 00:00:56, FastEthernet0/0
      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        10.0.2.0/30 is directly connected, FastEthernet0/0
L        10.0.2.2/32 is directly connected, FastEthernet0/0
      192.168.1.0/32 is subnetted, 1 subnets
C        192.168.1.1 is directly connected, Loopback0

Stub2#

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我們可以調整所有的路由器的 cdp timer 及 cdp holdtime 增快收斂速度...
預設 cdp timer 為每 60 秒送出...持續 180 秒若沒更新的話, 就 drop 掉...

Rack1R4# show cdp interface
FastEthernet0/0 is up, line protocol is up
  Encapsulation ARPA
  Sending CDP packets every 60 seconds
  Holdtime is 180 seconds
FastEthernet0/1 is up, line protocol is up
  Encapsulation ARPA
  Sending CDP packets every 60 seconds
  Holdtime is 180 seconds
Serial0/1 is up, line protocol is up
  Encapsulation HDLC
  Sending CDP packets every 60 seconds
  Holdtime is 180 seconds

Rack1R4# config t
Enter configuration commands, one per line.  End with CNTL/Z.
Rack1R4(config)# cdp timer ?
  <5-254>  Rate at which CDP packets are sent (in  sec)
Rack1R4(config)# cdp timer 5                  
Rack1R4(config)# cdp holdtime ?
  <10-255>  Length  of time  (in sec) that receiver must keep this packet
Rack1R4(config)# cdp holdtime 10
Rack1R4(config)# exit

Rack1R4# show cdp interface
FastEthernet0/0 is up, line protocol is up
  Encapsulation ARPA
  Sending CDP packets every 5 seconds
  Holdtime is 10 seconds
FastEthernet0/1 is up, line protocol is up
  Encapsulation ARPA
  Sending CDP packets every 5 seconds
  Holdtime is 10 seconds
Serial0/1 is up, line protocol is up
  Encapsulation HDLC
  Sending CDP packets every 5 seconds
  Holdtime is 10 seconds
Rack1R4#
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Cisco IOS Software Releases 12.4 T - Configuration Guides
IP Routing: ODR Configuration Guide, Cisco IOS Release 12.4T
http://www.cisco.com/en/US/docs/ios-xml/ios/iproute_odr/configuration/12-4t/ird-12-4t-book.html