Network-operations

 

BGP

“BGP Communities – Customer Guide”

What Is Common vs Optional

Feature	Common
Blackhole	✅ Almost universal
Local-pref TE	✅ Very common
ISP prepend	✅ Common
No-export	✅ Universal
Graceful shutdown	⚠️ Increasing
Geo-based control	⚠️ Large ISPs
Customer MED control	❌ Rare

Prefix tag - 

used to avoid re-distribution loops while doing mutual re-distribution

IP SLA - 

track service availability (like ping to 8.8.8.8) and switch to other route. this is applied on static route also if we have 2 ISPs and if we want auto switch-over

OSPF safe Drain -

 use max-metric router-lsa

BGP safe drain - 

1.Advertise a high MED value:

router bgp 65101

max-med administrative 10000

2.Use the BGP community GRACEFUL_SHUTDOWN (RFC8326):

router bgp 65101

graceful-shutdown

BFD

Enterprise dual ISP

1️⃣ IP SLA triggers
2️⃣ Local-pref drop
3️⃣ Default route withdrawn
4️⃣ Neighbor shutdown if needed

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DC leaf / border maintenance

1️⃣ OSPF max-metric
2️⃣ BGP graceful-shutdown community
3️⃣ AS-path prepend
4️⃣ Route withdrawal

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ISP / large SP

1️⃣ Prefix tagging
2️⃣ IGP max-metric
3️⃣ GSH community
4️⃣ Route reflection aware drain

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✅ Real-world maintenance philosophy

Don’t break adjacency
Drain before withdraw
IGP first, EGP second
Data-plane signals > link state