[300-135]新题

saga

Two routers are connected through PPP connection. After the PPP was established, the admin put OSPF running above it. The OSPF formed adjacency but after soon, the adjacnecy dropped. What is the reason?

Answer: GRE tunnel destination MUST not BE reachable through the tunnel

怎么会是not呢？应该是tunnel destination must be rechable through the tunnel吧？

5916991

题目问造成邻接关系断掉的原因，此答案说的 通过Tunnel，tunnel destination不可达。   因为tunnel目的不可达，所以邻接关系断掉，逻辑没毛病

junyi_de

这道题最根本的原因是recursive lookup, 当你在tunnel上开启路由协议的时候， tunnel source and destination address 不能宣告进路由协议，否则需要建立tunnel的地址从tunnel学到，导致cef查询递归死循环，路由邻居就会down掉。

一般解决这种可以有以下方案：
1. underlay走静态路由
2. underlay和overlay用vrf分隔开，也就是所谓的front-vrf

saga

谢谢各位大拿

q466265670

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