在我在 Cisco 6500（带有两个 SUP2T 卡）和另一个防火墙之间进行的捕获中，我可以看到 Cisco 路由器正在发送一个等于 0 的“转发状态”标志。
由于这是在初始化中并且在 RFC 中我们可以阅读：
https://www.rfc-editor.org/rfc/rfc4724
如果只想在计划重启时应用优雅重启（而不是计划重启和非计划重启），那么实现此目的的一种方法是在计划重启后将转发状态位设置为 1，并设置为 0其他情况。实现此目的的其他方法超出了本文档的范围。
这是否意味着 Cisco 只能支持 Planned Graceful-restart（即卡切换），而不能支持计划外（即 SUP2T 卡突然出现问题）。
Cisco 是否有任何理由在初始化时不发送等于 1 的“转发状态”标志？
谢谢你的帮助，
这是否意味着 Cisco 只能支持 Planned Graceful-restart（即卡切换）而不支持计划外（即 SUP2T 卡突然出现问题）？
不，这只是意味着 BGP 还没有重新启动。
引用RFC 4724 Graceful Restart Mechanism for BGP, pg 5：
Flags for Address Family:
This field contains bit flags relating to routes that were
advertised with the given AFI and SAFI.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|F| Reserved |
+-+-+-+-+-+-+-+-+
The most significant bit is defined as the Forwarding State (F)
bit, which can be used to indicate whether the forwarding state
for routes that were advertised with the given AFI and SAFI has
indeed been preserved during the previous BGP restart. When
set (value 1), the bit indicates that the forwarding state has
been preserved.
RFC 非常具体，何时Forwarding State设置，然后在“先前的 BGP 重启”期间保留路由。
另请参阅第 4.1 节：
To re-establish the session with its peer, the Restarting Speaker
MUST set the "Restart State" bit in the Graceful Restart Capability
of the OPEN message. Unless allowed via configuration, the
"Forwarding State" bit for an address family in the capability can be
set only if the forwarding state has indeed been preserved for that
address family during the restart.
我们再次看到（除了静态配置），“只有在重新启动期间确实为该地址族保留了转发状态”时，才应该设置转发状态位。