某公司由总部和分支机构构成，通过IPSec实现网络安全，网络拓扑结构如图4-1所示。

问题：

某公司由总部和分支机构构成，通过IPSec实现网络安全，网络拓扑结构如图4-1所示。
[*]
路由器之间的地址分配如表4-1所示。

总部端路由器的部分配置如下，解释配置中语句部分含义。
crypto isakmp policy 1 (1)
authentication pre-share (2)
group 2
crypto isakmp key test123 address 202.96.1.2 (3)
crypto ipsec transform-set VPNtag ah-md5-hmac esp-des (4)
crypto map VPNdemp 10 ipsec-isakmp
set peer 202.96.1.2 (5)
set transform-set VPNtag
match address 101
!
interface Tunnel0
ip address 192.168.1.1 255.255.255.0 (6)
no ip directed-broadcast
tunnel source 202.96.1.1
tunnel destination 202.96.1.2 (7)
crypto map VPNdemo
interface serial0/0
ip address 202.96.1.1 255.255.255.252
no ip directed-broadcast
crypto map VPNdemo (8)
!
interface Ethernet0/1
ip address 168.1.1.1 255.255.255.0
no ip directed-broadcast
interface Ethernet0/0
ip address 172.22.1.100 255.255.255.0
no ip directed-broadcast
!
ip classless
ip route 0.0.0.0 0.0.0.0 202.96.1.2 (9)
ip route 172.22.2.0 255.255.0.0 192.168.1.2 (10)
access-lost 101 permit gre host 202.96.1.1 host 202.96.1.2