Calico作为k8s的一个流行网络插件，它依赖BGP路由协议实现集群节点上的POD路由互通；而路由互通的前提是节点间建立 BGP Peer 连接。BGP 路由反射器（Route Reflectors，简称 RR）可以简化集群BGP Peer的连接方式，它是解决BGP扩展性问题的有效方式；具体来说：
- 没有 RR 时，所有节点之间需要两两建立连接（IBGP全互联），节点数量增加将导致连接数剧增、资源占用剧增
- 引入 RR 后，其他 BGP 路由器只需要与它建立连接并交换路由信息，节点数量增加连接数只是线性增加，节省系统资源
calico-node 版本 v3.3 开始支持内建路由反射器，非常方便，因此使用 calico 作为网络插件可以支持大规模节点数的K8S集群。
本文档主要讲解配置 BGP Route Reflectors，建议首先阅读基础calico文档。
前提条件
实验环境为按照kubeasz安装的2主2从集群，calico 版本 v3.3.2
$ kubectl get node
NAME STATUS ROLES AGE VERSION
192.168.1.1 Ready,SchedulingDisabled master 178m v1.13.1
192.168.1.2 Ready,SchedulingDisabled master 178m v1.13.1
192.168.1.3 Ready node 178m v1.13.1
192.168.1.4 Ready node 178m v1.13.1
$ kubectl get pod -n kube-system -o wide | grep calico
calico-kube-controllers-77487546bd-jqrlc 1/1 Running 0 179m 192.168.1.3 192.168.1.3 <none> <none>
calico-node-67t5m 2/2 Running 0 179m 192.168.1.1 192.168.1.1 <none> <none>
calico-node-drmhq 2/2 Running 0 179m 192.168.1.2 192.168.1.2 <none> <none>
calico-node-rjtkv 2/2 Running 0 179m 192.168.1.4 192.168.1.4 <none> <none>
calico-node-xtspl 2/2 Running 0 179m 192.168.1.3 192.168.1.3 <none> <none>
查看当前集群中BGP连接情况：可以看到集群中4个节点两两建立了 BGP 连接
$ ansible all -m shell -a ‘/opt/kube/bin/calicoctl node status‘
192.168.1.3 | SUCCESS | rc=0 >>
Calico process is running.
IPv4 BGP status
+--------------+-------------------+-------+----------+-------------+
| PEER ADDRESS | PEER TYPE | STATE | SINCE | INFO |
+--------------+-------------------+-------+----------+-------------+
| 192.168.1.1 | node-to-node mesh | up | 03:08:20 | Established |
| 192.168.1.2 | node-to-node mesh | up | 03:08:18 | Established |
| 192.168.1.4 | node-to-node mesh | up | 03:08:19 | Established |
+--------------+-------------------+-------+----------+-------------+
IPv6 BGP status
No IPv6 peers found.
192.168.1.2 | SUCCESS | rc=0 >>
Calico process is running.
IPv4 BGP status
+--------------+-------------------+-------+----------+-------------+
| PEER ADDRESS | PEER TYPE | STATE | SINCE | INFO |
+--------------+-------------------+-------+----------+-------------+
| 192.168.1.4 | node-to-node mesh | up | 03:08:17 | Established |
| 192.168.1.3 | node-to-node mesh | up | 03:08:18 | Established |
| 192.168.1.1 | node-to-node mesh | up | 03:08:20 | Established |
+--------------+-------------------+-------+----------+-------------+
IPv6 BGP status
No IPv6 peers found.
192.168.1.1 | SUCCESS | rc=0 >>
Calico process is running.
IPv4 BGP status
+--------------+-------------------+-------+----------+-------------+
| PEER ADDRESS | PEER TYPE | STATE | SINCE | INFO |
+--------------+-------------------+-------+----------+-------------+
| 192.168.1.2 | node-to-node mesh | up | 03:08:21 | Established |
| 192.168.1.3 | node-to-node mesh | up | 03:08:21 | Established |
| 192.168.1.4 | node-to-node mesh | up | 03:08:21 | Established |
+--------------+-------------------+-------+----------+-------------+
IPv6 BGP status
No IPv6 peers found.
192.168.1.4 | SUCCESS | rc=0 >>
Calico process is running.
IPv4 BGP status
+--------------+-------------------+-------+----------+-------------+
| PEER ADDRESS | PEER TYPE | STATE | SINCE | INFO |
+--------------+-------------------+-------+----------+-------------+
| 192.168.1.2 | node-to-node mesh | up | 03:08:17 | Established |
| 192.168.1.3 | node-to-node mesh | up | 03:08:19 | Established |
| 192.168.1.1 | node-to-node mesh | up | 03:08:20 | Established |
+--------------+-------------------+-------+----------+-------------+
IPv6 BGP status
No IPv6 peers found.
配置全局禁用全连接（BGP full mesh）
$ cat << EOF | calicoctl create -f -
apiVersion: projectcalico.org/v3
kind: BGPConfiguration
metadata:
name: default
spec:
logSeverityScreen: Info
nodeToNodeMeshEnabled: false
asNumber: 64512
EOF
上述命令配置完成后，再次使用命令ansible all -m shell -a ‘/opt/kube/bin/calicoctl node status‘查看，可以看到之前所有的bgp连接都消失了。
配置 BGP node 与 Route Reflector 的连接建立规则
$ cat << EOF | calicoctl create -f -
kind: BGPPeer
apiVersion: projectcalico.org/v3
metadata:
name: peer-to-rrs
spec:
# 规则1：普通 bgp node 与 rr 建立连接
nodeSelector: "!has(i-am-a-route-reflector)"
peerSelector: has(i-am-a-route-reflector)
---
kind: BGPPeer
apiVersion: projectcalico.org/v3
metadata:
name: rr-mesh
spec:
# 规则2：route reflectors 之间也建立连接
nodeSelector: has(i-am-a-route-reflector)
peerSelector: has(i-am-a-route-reflector)
EOF
上述命令配置完成后，使用命令：calicoctl get bgppeer calicoctl get bgppeer rr-mesh -o yaml 检查配置是否正确。
选择并配置 Route Reflector 节点
首先查看当前集群中的节点：
$ calicoctl get node -o wide
NAME ASN IPV4 IPV6
k8s401 (64512) 192.168.1.1/24
k8s402 (64512) 192.168.1.2/24
k8s403 (64512) 192.168.1.3/24
k8s404 (64512) 192.168.1.4/24
可以在集群中选择1个或多个节点作为 rr 节点，这里先选择节点：k8s401
# 1.先导出 node k8s401 的配置，准备修改
$ calicoctl get node k8s401 --export -o yaml |tee rr01.yml
apiVersion: projectcalico.org/v3
kind: Node
metadata:
creationTimestamp: null
name: k8s401
spec:
bgp:
ipv4Address: 192.168.1.1/24
ipv4IPIPTunnelAddr: 172.20.7.128
orchRefs:
- nodeName: 192.168.1.1
orchestrator: k8s
# 2.修改上述 rr01.yml 的配置如下
apiVersion: projectcalico.org/v3
kind: Node
metadata:
creationTimestamp: null
name: k8s401
labels:
# 设置标签
i-am-a-route-reflector: true
spec:
bgp:
ipv4Address: 192.168.1.1/24
ipv4IPIPTunnelAddr: 172.20.7.128
# 设置集群ID
routeReflectorClusterID: 224.0.0.1
orchRefs:
- nodeName: 192.168.1.1
orchestrator: k8s
# 3.应用修改后的 rr node 配置
$ calicoctl apply -f rr01.yml
查看增加 rr 之后的bgp 连接情况
$ ansible all -m shell -a ‘/opt/kube/bin/calicoctl node status‘
192.168.1.4 | SUCCESS | rc=0 >>
Calico process is running.
IPv4 BGP status
+--------------+-----------+-------+----------+-------------+
| PEER ADDRESS | PEER TYPE | STATE | SINCE | INFO |
+--------------+-----------+-------+----------+-------------+
| 192.168.1.1 | node specific | up | 11:02:55 | Established |
+--------------+-----------+-------+----------+-------------+
IPv6 BGP status
No IPv6 peers found.
192.168.1.3 | SUCCESS | rc=0 >>
Calico process is running.
IPv4 BGP status
+--------------+-----------+-------+----------+-------------+
| PEER ADDRESS | PEER TYPE | STATE | SINCE | INFO |
+--------------+-----------+-------+----------+-------------+
| 192.168.1.1 | node specific | up | 11:02:55 | Established |
+--------------+-----------+-------+----------+-------------+
IPv6 BGP status
No IPv6 peers found.
192.168.1.1 | SUCCESS | rc=0 >>
Calico process is running.
IPv4 BGP status
+--------------+---------------+-------+----------+-------------+
| PEER ADDRESS | PEER TYPE | STATE | SINCE | INFO |
+--------------+---------------+-------+----------+-------------+
| 192.168.1.2 | node specific | up | 11:02:55 | Established |
| 192.168.1.3 | node specific | up | 11:02:55 | Established |
| 192.168.1.4 | node specific | up | 11:02:55 | Established |
+--------------+---------------+-------+----------+-------------+
IPv6 BGP status
No IPv6 peers found.
192.168.1.2 | SUCCESS | rc=0 >>
Calico process is running.
IPv4 BGP status
+--------------+-----------+-------+----------+-------------+
| PEER ADDRESS | PEER TYPE | STATE | SINCE | INFO |
+--------------+-----------+-------+----------+-------------+
| 192.168.1.1 | node specific | up | 11:02:55 | Established |
+--------------+-----------+-------+----------+-------------+
IPv6 BGP status
No IPv6 peers found.
可以看到所有其他节点都与所选rr节点建立bgp连接。
再增加一个 rr 节点
步骤同上述选择第1个 rr 节点，这里省略；添加成功后可以看到所有其他节点都与两个rr节点建立bgp连接，两个rr节点之间也建立bgp连接。
- 对于节点数较多的
K8S集群建议配置3-4个 RR 节点