2009-05-08

Question of the day

вопрос:
дана топология:


конфиг роутеров:
R1

hostname R1
int fa0/0
descr to R2
no shu
int fa0/0.10
enca dot 10
ip add 10.0.10.1 255.255.255.0
router eigrp 1
network 10.0.10.0 255.255.255.0


R2

hostname R2
int fa0/0
descr to R1
no shu
int fa0/0.10
enca dot 10
ip add 10.0.10.2 255.255.255.0
router eigrp 1
network 10.0.10.0 255.255.255.0
redistribute static metric 1000 2500 255 1 1500
ip route 10.255.255.0 255.255.255.0 null0


вопрос: какой FD будет у маршрута в сеть 10.255.255.0/24 на R1?

ответ: приблизительно 921600

R1#sh ip ro 10.255.255.0
Routing entry for 10.255.255.0/24
Known via "eigrp 2", distance 170, metric 921600, type external
Redistributing via eigrp 2
Last update from 10.0.20.2 on FastEthernet0/0.20, 00:00:30 ago
Routing Descriptor Blocks:
* 10.0.20.2, from 10.0.20.2, 00:00:30 ago, via FastEthernet0/0.20
Route metric is 921600, traffic share count is 1
Total delay is 26000 microseconds, minimum bandwidth is 10000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 1



усложним задачу, добавим в конфиг роутеров:
R1

int fa0/0.20
enca dot 20
ip add 10.0.20.1 255.255.255.0
router eigrp 2
network 10.0.20.0 255.255.255.0


R2

int fa0/0.20
enca dot 20
ip add 10.0.20.2 255.255.255.0
router eigrp 2
network 10.0.20.0 255.255.255.0
redistribute static metric 100000 2500 255 1 1500


вопрос: какой теперь будет FD маршрута в сеть 10.255.255.0/24 на R1?

ответ: все тот же

R1#sh ip ro 10.255.255.0
Routing entry for 10.255.255.0/24
Known via "eigrp 1", distance 170, metric 921600, type external
Redistributing via eigrp 1
Last update from 10.0.10.2 on FastEthernet0/0.10, 00:00:58 ago
Routing Descriptor Blocks:
* 10.0.10.2, from 10.0.10.2, 00:00:58 ago, via FastEthernet0/0.10
Route metric is 921600, traffic share count is 1
Total delay is 26000 microseconds, minimum bandwidth is 10000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 1
R1#sh ip ei topo 1 10.255.255.0 255.255.255.0
IP-EIGRP (AS 1): Topology entry for 10.255.255.0/24
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 921600
Routing Descriptor Blocks:
10.0.10.2 (FastEthernet0/0.10), from 10.0.10.2, Send flag is 0x0
Composite metric is (921600/896000), Route is External
Vector metric:
Minimum bandwidth is 10000 Kbit
Total delay is 26000 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 1
External data:
Originating router is 10.0.10.2
AS number of route is 0
External protocol is Static, external metric is 0
Administrator tag is 0 (0x00000000)
R1#sh ip ei topo 2 10.255.255.0 255.255.255.0
IP-EIGRP (AS 2): Topology entry for 10.255.255.0/24
State is Passive, Query origin flag is 1, 0 Successor(s), FD is 4294967295
Routing Descriptor Blocks:
10.0.20.2 (FastEthernet0/0.20), from 10.0.20.2, Send flag is 0x0
Composite metric is (921600/665600), Route is External
Vector metric:
Minimum bandwidth is 10000 Kbit
Total delay is 26000 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 1
External data:
Originating router is 10.0.10.2
AS number of route is 0
External protocol is Static, external metric is 0
Administrator tag is 0 (0x00000000)


продолжим эксперимент :)
отключим на R2 подынтерфейс принадлежащий eigrp1:

R2(config)#int fa0/0.10
R2(config-subif)#shu

через буквально 10-15 секунд R1 обнаружит потерю соседа, и сменит маршрут в сеть 10.255.255.0/24:

*Mar 1 00:23:10.699: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.0.10.2 (FastEthernet0/0.10) is down: holding time expired
R1#sh ip ro 10.255.255.0
Routing entry for 10.255.255.0/24
Known via "eigrp 2", distance 170, metric 921600, type external
Redistributing via eigrp 2
Last update from 10.0.20.2 on FastEthernet0/0.20, 00:00:30 ago
Routing Descriptor Blocks:
* 10.0.20.2, from 10.0.20.2, 00:00:30 ago, via FastEthernet0/0.20
Route metric is 921600, traffic share count is 1
Total delay is 26000 microseconds, minimum bandwidth is 10000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 1


вопрос: какой маршрут будет активным на R1, если на R2 поднять подынтерфейс fa0/0.10?
ответ: вернется маршрут процесса eigrp1:

R2(config)#int fa0/0.10
R2(config-subif)#no shu
*Mar 1 00:25:03.815: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.0.10.2 (FastEthernet0/0.10) is up: new adjacency
R1#sh ip ro 10.255.255.0
Routing entry for 10.255.255.0/24
Known via "eigrp 1", distance 170, metric 921600, type external
Redistributing via eigrp 1
Last update from 10.0.10.2 on FastEthernet0/0.10, 00:00:58 ago
Routing Descriptor Blocks:
* 10.0.10.2, from 10.0.10.2, 00:00:58 ago, via FastEthernet0/0.10
Route metric is 921600, traffic share count is 1
Total delay is 26000 microseconds, minimum bandwidth is 10000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 1

Немає коментарів: