直接连接路由器是否需要DHCP中继的路由协议才能工作？

Question

假设我们有R01、R02和R03相互连接，它们分别连接到不同的子网SUB01、SUB02和SUB03。R03被设置为DHCP服务器，DHCP在其自己的子网中对工作站很好地工作。现在，我们使用一个IP助手地址R01和R02来设置R03，其中每个地址都是连接的。假设所有配置都是正确的。Do，我们需要为DHCP和DHCP中继配置路由协议，以实现它们的魔力？或者它们应该在这些配置中正常工作吗？

UPDATE (28APR2023):

这里有一个例子，说明了所有正在运行的路由器的信任以及路由表的情况。还有，下面是到数据包跟踪器文件的链接。

R01(config)#do sh run
Building configuration...

Current configuration : 787 bytes
!
version 15.1
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname R01
!
!
!
!
!
!
!
!
ip cef
no ipv6 cef
!
!
!
!
license udi pid CISCO2911/K9 sn FTX1524X850-
!
!
!
!
!
!
!
!
!
!
!
spanning-tree mode pvst
!
!
!
!
!
!
interface GigabitEthernet0/0
 ip address 192.168.0.30 255.255.255.224
 ip helper-address 192.168.0.254
 duplex auto
 speed auto
!
interface GigabitEthernet0/1
 ip address 192.168.0.126 255.255.255.224
 duplex auto
 speed auto
!
interface GigabitEthernet0/2
 ip address 192.168.0.253 255.255.255.224
 duplex auto
 speed auto
!
interface Vlan1
 no ip address
 shutdown
!
ip classless
!
ip flow-export version 9
!
!
!
!
!
!
!
line con 0
 exec-timeout 0 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end


----------------------


R01(config)#do sh 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, E - EGP
       i - IS-IS, 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

     192.168.0.0/24 is variably subnetted, 6 subnets, 2 masks
C       192.168.0.0/27 is directly connected, GigabitEthernet0/0
L       192.168.0.30/32 is directly connected, GigabitEthernet0/0
C       192.168.0.96/27 is directly connected, GigabitEthernet0/1
L       192.168.0.126/32 is directly connected, GigabitEthernet0/1
C       192.168.0.224/27 is directly connected, GigabitEthernet0/2
L       192.168.0.253/32 is directly connected, GigabitEthernet0/2

========================

R02(config)#do sh run
Building configuration...

Current configuration : 787 bytes
!
version 15.1
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname R02
!
!
!
!
!
!
!
!
ip cef
no ipv6 cef
!
!
!
!
license udi pid CISCO2911/K9 sn FTX1524U1U3-
!
!
!
!
!
!
!
!
!
!
!
spanning-tree mode pvst
!
!
!
!
!
!
interface GigabitEthernet0/0
 ip address 192.168.0.62 255.255.255.224
 ip helper-address 192.168.0.189
 duplex auto
 speed auto
!
interface GigabitEthernet0/1
 ip address 192.168.0.125 255.255.255.224
 duplex auto
 speed auto
!
interface GigabitEthernet0/2
 ip address 192.168.0.190 255.255.255.224
 duplex auto
 speed auto
!
interface Vlan1
 no ip address
 shutdown
!
ip classless
!
ip flow-export version 9
!
!
!
!
!
!
!
line con 0
 exec-timeout 0 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end


----------------------


R02(config)#do sh 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, E - EGP
       i - IS-IS, 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

     192.168.0.0/24 is variably subnetted, 6 subnets, 2 masks
C       192.168.0.32/27 is directly connected, GigabitEthernet0/0
L       192.168.0.62/32 is directly connected, GigabitEthernet0/0
C       192.168.0.96/27 is directly connected, GigabitEthernet0/1
L       192.168.0.125/32 is directly connected, GigabitEthernet0/1
C       192.168.0.160/27 is directly connected, GigabitEthernet0/2
L       192.168.0.190/32 is directly connected, GigabitEthernet0/2

============================

R03(config)#do sh run
Building configuration...

Current configuration : 1125 bytes
!
version 15.1
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname R03
!
!
!
!
ip dhcp excluded-address 192.168.0.30
ip dhcp excluded-address 192.168.0.62
ip dhcp excluded-address 192.168.0.94
!
ip dhcp pool SUB01
 network 192.168.0.0 255.255.255.224
 default-router 192.168.0.30
ip dhcp pool SUB02
 network 192.168.0.32 255.255.255.224
 default-router 192.168.0.62
ip dhcp pool SUB03
 network 192.168.0.64 255.255.255.224
 default-router 192.168.0.94
!
!
!
ip cef
no ipv6 cef
!
!
!
!
license udi pid CISCO2911/K9 sn FTX15244VUL-
!
!
!
!
!
!
!
!
!
!
!
spanning-tree mode pvst
!
!
!
!
!
!
interface GigabitEthernet0/0
 ip address 192.168.0.94 255.255.255.224
 duplex auto
 speed auto
!
interface GigabitEthernet0/1
 ip address 192.168.0.254 255.255.255.224
 duplex auto
 speed auto
!
interface GigabitEthernet0/2
 ip address 192.168.0.189 255.255.255.224
 duplex auto
 speed auto
!
interface Vlan1
 no ip address
 shutdown
!
ip classless
!
ip flow-export version 9
!
!
!
!
!
!
!
line con 0
 exec-timeout 0 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end



----------


 
    
R03(config)#do sh 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, E - EGP
       i - IS-IS, 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

     192.168.0.0/24 is variably subnetted, 6 subnets, 2 masks
C       192.168.0.64/27 is directly connected, GigabitEthernet0/0
L       192.168.0.94/32 is directly connected, GigabitEthernet0/0
C       192.168.0.160/27 is directly connected, GigabitEthernet0/2
L       192.168.0.189/32 is directly connected, GigabitEthernet0/2
C       192.168.0.224/27 is directly connected, GigabitEthernet0/1
L       192.168.0.254/32 is directly connected, GigabitEthernet0/1



=====================

Answer 1

路由器需要知道如何到达网络，以便向这些网络发送数据包。DHCP中继正在向其他网络发送数据包。路由器通过三种方式学习路由：

• 直接连接网络
• 静态配置路由
• 来自路由协议的动态路由

由于R1和R2网络没有直接连接到R3，R3要么需要静态配置的路由指向各自的R1路由器和R2路由器，要么需要运行通用路由协议来交换路由信息。

路由器根据其路由表中的内容路由数据包。路由协议不路由数据包，它们被邻居路由器用来交换路由信息，以帮助填充它们的路由表。

关于您的评论的Edit：

请记住，DHCP适用于请求/响应。你的评论：

不是SUB01和SUB02，而是R01和R02。例如，PC1不需要知道R03在哪里。只是广播而已。这样做时，R01不应该丢弃DHCP数据包，因为IP helper-address是在R01的端口G0/0 (192.168.0.30/27)上配置的，而D19端口D18又将<#>directly连接到R03 ( DHCP )。这就是DHCP继电器的全部想法。对，是这样?

不解决R3需要向PC1发送DHCP响应这一事实，R3也不知道如何到达PC1网络(其中DHCP中继在接口上使用该网络中的地址进行配置)，因此R3删除DHCP响应数据包，因为它在其路由表中找不到到达目标网络的路径。

是的，PC1广播DHCP请求，但是来自R3的单播响应需要转到PC1连接的R1接口的地址。

并不是所有的广播都像你所说的那样。广播不跨路由器。PC1广播DHCP请求，即使DHCP服务器位于同一网络上，来自DHCP服务器的响应也是单播。DHCP中继只需捕获广播并将单播请求发送到DHCP服务器，接收单播响应作为回报。这在您的场景中不会发生，因为DHCP中继地址是配置DHCP中继的接口网络中的接口地址。

只需在所有三个路由器上放置以下命令即可配置路由协议：

router ospf 1
 network 0.0.0.0 255.255.255.255 area 0
!

这将启动OSPF并包括OSPF进程中的所有路由器接口。如果您想在PC网络上阻止OSPF hellos (一种良好的实践)，只需添加：

passive-interface GigabitEthernet0/0

您也可以在每个路由器上配置静态路由，但这有点复杂，而且不会扩展。