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36 lines
2.3 KiB
Plaintext
36 lines
2.3 KiB
Plaintext
// Module included in the following assemblies:
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//
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// * networking/metallb/about-metallb.adoc
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:_mod-docs-content-type: CONCEPT
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[id="nw-metallb-bgp-limitations_{context}"]
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= Limitations for BGP mode
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[role="_abstract"]
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In {product-title}, MetalLB border gateway protocol (BGP) mode can reset active connections when a BGP session terminates and requires a single ASN and router ID for all BGP peers. Use a node selector when adding a BGP peer to limit which nodes run BGP sessions and reduce the impact of node faults.
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[id="nw-metallb-bgp-limitations-break-connections_{context}"]
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== Node failure can break all active connections
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MetalLB shares a limitation that is common to BGP-based load balancing.
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When a BGP session terminates, such as when a node fails or when a `speaker` pod restarts, the session termination might result in resetting all active connections.
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End users can experience a `Connection reset by peer` message.
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The consequence of a terminated BGP session is implementation-specific for each router manufacturer.
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However, you can anticipate that a change in the number of `speaker` pods affects the number of BGP sessions and that active connections with BGP peers will break.
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To avoid or reduce the likelihood of a service interruption, you can specify a node selector when you add a BGP peer.
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By limiting the number of nodes that start BGP sessions, a fault on a node that does not have a BGP session has no affect on connections to the service.
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[id="nw-metallb-bgp-limitations-single-asn_{context}"]
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== Support for a single ASN and a single router ID only
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When you add a BGP peer custom resource, you specify the `spec.myASN` field to identify the Autonomous System Number (ASN) that MetalLB belongs to.
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{product-title} uses an implementation of BGP with MetalLB that requires MetalLB to belong to a single ASN.
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If you attempt to add a BGP peer and specify a different value for `spec.myASN` than an existing BGP peer custom resource, you receive an error.
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Similarly, when you add a BGP peer custom resource, the `spec.routerID` field is optional.
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If you specify a value for this field, you must specify the same value for all other BGP peer custom resources that you add.
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The limitation to support a single ASN and single router ID is a difference with the community-supported implementation of MetalLB.
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