JunOS Dynamic Neighbors With Different Peer-AS
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Authored by cmooney on May 11 2022, 2:01 PM.

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	F35130397: JunOS Dynamic Neighbors With Different Peer-AS
	May 11 2022, 2:01 PM

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	# AS-Path definitons as follows:

	set policy-options as-path K8S ".* (64601\|64602)$"
	set policy-options as-path LVS ".* 64600$"
	set policy-options as-path K8S_STAGE ".* (64603\|64604)$"
	set policy-options as-path K8S_MLSTAGE ".* 64608$"
	set policy-options as-path K8S_MLSERVE ".* (64606\|64607)$"
	set policy-options as-path ANYCAST ".* 64604$"

	# AS-Path list is defined to match all our potential end-host peers:

	set policy-options as-list SERVER_BGP members 64600-64609

	# BGP Groups are defined with 'dynamic-neighbor' configured for the whole private subnet, and the "peer-as-list" command (note vQFX insisted on also having 'peer-as' defined, but doesn't seem to matter):

	cathal@LSW1> show configuration routing-instances WMF_PROD protocols bgp
	group DYNAMIC_PEERS_V4 {
	type external;
	import SERVER_BGP_IN;
	family inet {
	unicast;
	}
	authentication-key "$9$aCUqf0ORcrvQFEyleXxjHqfF/tuOIhS9C"; ## SECRET-DATA
	export DEFAULT_EVPN;
	peer-as 10;
	local-as 14907 loops 2 private no-prepend-global-as;
	dynamic-neighbor RACK_E1 {
	allow 198.18.101.0/24;
	}
	dynamic-neighbor ROW_E {
	allow 198.18.201.0/24;
	}
	peer-as-list SERVER_BGP;
	}
	group DYNAMIC_PEERS_V6 {
	type external;
	import SERVER_BGP_IN;
	family inet6 {
	unicast;
	}
	authentication-key "$9$d7saU3nCpORikA0B1yr24aUkPQFn9tuf5"; ## SECRET-DATA
	export DEFAULT_EVPN;
	peer-as 10;
	local-as 14907 loops 2 private no-prepend-global-as;
	dynamic-neighbor RACK_E1 {
	allow 2001:470:6a7f:91::/64;
	}
	dynamic-neighbor ROW_E {
	allow 2001:470:6a7f:90::/64;
	}
	peer-as-list SERVER_BGP;
	}
	local-as 65187;

	# With this config BGP establishes to separate peers on the same subnet using different ASNs:

	cathal@LSW1> show bgp summary instance WMF_PROD \| find ^Peer
	Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State\|#Active/Received/Accepted/Damped...
	198.18.101.10 64600 125 135 0 0 1:00:01 Establ
	WMF_PROD.inet.0: 1/1/1/0
	198.18.101.11 64601 72 78 0 0 33:27 Establ
	WMF_PROD.inet.0: 1/1/1/0
	2001:470:6a7f:91::10 64600 107 116 0 0 51:46 Establ
	WMF_PROD.inet6.0: 1/1/1/0
	2001:470:6a7f:91::11 64601 72 79 0 0 33:27 Establ
	WMF_PROD.inet6.0: 1/1/1/0


	# The SERVER-BGP-IN policy is defined as follows, combining the terms from our existing policies into one, but matching on the AS-path in each:

	cathal@LSW1> show configuration policy-options policy-statement SERVER_BGP_IN
	term lvs_service_ips {
	from {
	family inet;
	protocol bgp;
	as-path LVS;
	prefix-list-filter LVS-service-ips orlonger;
	}
	then accept;
	}
	term lvs_service_ips6 {
	from {
	family inet6;
	protocol bgp;
	as-path LVS;
	prefix-list-filter LVS-service-ips6 orlonger;
	}
	then accept;
	}
	term kubernetes_ipv4 {
	from {
	family inet;
	protocol bgp;
	as-path K8S;
	prefix-list-filter kubernetes-ipv4 orlonger;
	}
	then {
	local-preference 163;
	accept;
	}
	}
	term kubernetes_ipv6 {
	from {
	family inet6;
	protocol bgp;
	as-path K8S;
	prefix-list-filter kubernetes-ipv6 orlonger;
	}
	then accept;
	}
	then reject;


	The policy only affects what we want, for instance the local-pref set to 163 we only see on the route from AS 64601:

	cathal@LSW1> show route protocol bgp table WMF_PROD.inet.0 terse

	WMF_PROD.inet.0: 15 destinations, 16 routes (15 active, 0 holddown, 0 hidden)
	@ = Routing Use Only, # = Forwarding Use Only
	+ = Active Route, - = Last Active, * = Both

	A V Destination P Prf Metric 1 Metric 2 Next hop AS path
	* ? 1.2.3.4/32 B 170 100 0 64600 ?
	unverified >198.18.101.10
	* ? 3.4.5.6/32 B 170 163 0 64601 ?
	unverified >198.18.101.11

Event Timeline

cmooney created this paste.May 11 2022, 2:01 PM

cmooney mentioned this in T306649: Agree strategy for Kubernetes BGP peering to top-of-rack switches.May 11 2022, 3:04 PM

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JunOS Dynamic Neighbors With Different Peer-AS
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