unicast EIGRP peering
wide metric
leak-map
add-path
address-family
IP FRR/fast reroute(single hop)
unicast EIGRP peering
正常情况下，EIGRP是通过组播建立邻居的，但是在限制组播的链路上就可以使用单播建立邻居。
应用场景：
1.若XXX中不允许组播流量
2.以太网中限制邻居数量，不让其自动建立邻居
举例：
只想让R1与R3建立邻居，那么就可以采取单播建立邻居
R1:neighbor 192.168.1.3 f0/0
R3：neighbor 192.168.1.1 f0/0
注意：若是network后，配置了上述命令，一样采取单播，不使用组播
wide metric
classic metric采取32位表示metric
接口带宽超过10G,则metric值固定是256，可能导致不理想的等价负载均衡。
为了避免上述问题，wide宽度量值采取64bit来计算高带宽的metric。
The 64-bit metric calculations work only in EIGRP named mode. EIGRP classic mode uses 32-bit metric calculations.
K1 = K3 = 1 K2 = K4 = K5 = 0 K6 = 0
Device-A(config)# router eigrp name
Device-A(config-router)# metrics version 64bit
Device-A(config-router)# address-family ipv4 autonomous-system 100
Device-A(config-router-af)# metric weights 0 0 0 1 0 0 1
比例因子：
计算高链路，使用64位计算的，但是在数据包报头里还是采取32位表示metric，这个时候就需要转换，称为比例因子，64位/比例因子，放置到32位即可，范围1-255，默认是128
Router(config-router-af)# metric rib-scale scale value Router(config-router-af)# no metric rib-scale scale value
leak-map：泄露部分子网路由
举例：
Example 1: eigrp stub leak-map Command
Router(config)# router eigrp 1
Router(config-router)# eigrp stub leak-map route-map
Example 2: ip summary-address eigrp
Router(config)# interface Serial 0/0
Router(config-if)# ip summary-address eigrp 1 10.0.0.0 255.0.0.0 leak-map route-map1
add-path
在DM XXX网络中允许hub提供多条最佳路径
比如spoke1传递给hub1，hub1也只会选择一条路径传递给spoke3与4的
配置命令：
enable
config terminal
router eigrp name
address-family ipv4/6（若是选择IPV6，那么必须先配置ipv6 unicast-routing） autonomous-system as-number
af-interface{default|interface-type interface-number}
af-interface只是新版的IOS将功能都集中在一个进程下，比如interface tunnel0与af-interface tunnel0是一致的
no next-hop-self{no-ecmp-mode}
add-paths number 最大是4
end
show running-config
address-family
configures an IPv4 address-family session for the VRF named RED
Router(config)# ip vrf RED
Router(config-vrf)# rd 1:1
Router(config-vrf)# exit
Router(config)# router eigrp 1
Router(config-router)# address-family ipv4 vrf RED
Router(config-router-af)# autonomous-system 101
Router(config-router-af)# network 172.16.0.0
Router(config-router-af)#default-metric 10000 100 255 1 1500
Router(config-router-af)# exit-address-family
configures a non-VRF address-family
Router(config)# router eigrp virtual-name
Router(config-router)# address-family ipv4 autonomous-system 3
Router(config-router-af)# network 10.0.0.0 0.0.0.255
configures a non-VRF address-family
Router(config)# router eigrp virtual-name
Router(config-router)# address-family ipv6 autonomous-system 3
Router(config-router-af)# network 2001:1::/64
IP FRR
EIGRP Loop-free Alternate Fast Reroute
EIGRP的无环路备用快速重路由功能允许EIGRP通过预先计算修复路径或备份路由，在链路失效时，过渡时间小于50ms，预先将计算好的修复路径或备份路径路由添加到routing information base中。
Information About EIGRP Loop-Free Alternate Fast Reroute Repair Paths Overview
路由过渡：当链路或设备发生故障，运行路由算法计算新的路径。在计算过程中，源和目的地之间的连接被中断。
当链路或设备发生故障时，最初只有相邻的设备知道，网络中的所有其它设备都没有意识到这种故障的性质和位置，直到这个故障信息通过路由协议传播。这种信息的传播可能需要几百毫秒。
路由协议在预期的故障预先计算修复路径，在检测出故障的时刻，使得修复路径可以被激活时。在EIGRP网络，预计算的修复路径或备份路由被称为可行后继或无环的交替（LFAS）。
LFA Computation
1）Per-link (link-based) computation:
link-based的方法只保护下一跳地址。它不需要保护目标节点。这种方法是不理想的，这种方法要求主链路的所有流量被重定向到下一跳，而不是被分散在多条路径。重定向所有流量到下一跳可能导致链路拥塞
2）Per-prefix (prefix-based) computation:
prefix-based允许计算每个前缀的备份信息从而保护的目的地址。
EIGRP 使用 prefix-based 计算LFAs.
EIGRP 使用DUAL计算successor和feasible successors.
EIGRP使用successor作为主路径，feasible successors作为修复路径或LFAs
LFA Tie-Breaking Rules
当一条主路径有多条备份路径，EIGRP使用tie-breaking rule 为每一个前缀的主路径选择一条LFA。
Interface-disjoint ：Eliminates LFAs that share the outgoing interface with the protected path.
优先消除与主路径相同出接口的路径
Linecard-disjoint：Eliminates LFAs that share the line card with the protected path.
优先消除与主路径共享线路的路径
Lowest-repair-path-metric：Eliminates LFAs whose metric to the protected prefix is high. Multiple LFAs with the same lowest path metric may remain in the routing table after this tie-breaker is applied.
存在多条路径，优先消除metric值大的
Shared Risk Link Group (SRLG)-disjoint：Eliminates LFAs that belong to any of the protected path SRLGs.
SRLGs refer to situations where links in a network share a common fiber (or a common physical attribute). If one link fails, other links in the group may also fail. Therefore, links in a group share risks.
优先消除与主路径有相同物理属性（速率，材质等）的链路
Configure loop-free alternate (LFA) Fast Reroutes (FRRs) per prefix in EIGRP
使用上述规则选路，必须先关闭负载均衡的功能
当主路径是具有多个LFAs的等价路径(ECMP)路径时，前缀(网络)在LFAs之间均匀分布，因为ECMP路径的默认行为是负载共享。但是，通过启用连接断开配置来控制LFAs的选择。要启用连接断开配置，先关闭负载均衡的功能。
enabling Tie-Breaking Rules for EIGRP LFAs
Priority number assigned to the tie-breaking attribute. The range is from 1 to 255.
The default attributes and their associated priorities are used to determine the LFA.
interface-disjoint—20
linecard-disjoint—40
lowest-backup-path-metric—30
srlg-disjoint—10
The lower the configured priority value the higher the priority of the tie-breaking attribute.
官方文档说明
Use this command to configure tie-breaking rules when there are multiple LFAs for a given primary path. EIGRP allows you to use four attributes to configure tie-breaking rules. Each of the following keywords specifies an attribute and allows you to configure a tie-breaking rule based on the attribute: interface-disjoint, linecard-disjoint, lowest-backup-path-metric, and srlg-disjoint. You can configure a priority value for each attribute. Tie-breaking rules are applied on the basis of the priority configured for each attribute. The lower the configured priority value the higher the priority of the tie-breaking attribute.
1.启用快速重路由功能
Device> enable
Device# configure terminal
Device(config)# router eigrp name
Device(config-router)# address-family ipv4 autonomous-system 1
Device(config-router-af)# topology base
Device(config-router-af-topology)# fast-reroute per-prefix route-map map1
Device(config-router-af-topology)# end
2.关闭负载均衡功能，以及定义不同规则的优先级
Device> enable
Device# configure terminal
Device(config)# router eigrp name
Device(config-router)# address-family ipv4 autonomous-system 1
Device(config-router-af)# topology base
Device(config-router-af-topology)# fast-reroute load-sharing disable
Device(config-router-af-topology)# fast-reroute tie-break interface-disjoint 2
Device(config-router-af-topology)# fast-reroute tie-break srlg-disjoint 1
Device(config-router-af-topology)# fast-reroute tie-break linecard-disjoint 3
Device(config-router-af-topology)# fast-reroute tie-break lowest-backup-path-metric 4
