What Is the Purpose of Setting the DN Bit in an OSPF LSA?

Adamcolob · Created Apr 19, 2017 07:38:57

If a Provider Edge (PE) device advertises Type-3 and 5 link-state advertisements (LSAs) to Customer Edge (CE) devices through area 0, the optional high-order bit of these LSAs must be set and called the DN bit. If these LSAs are advertised through an area other than area 0, the DN bit can be set or not set.

The DN bit is used to prevent routing loops. A PE ignores any LSA whose DN bit is set. This prevents a routing loop caused when a PE learns from the CE the LSA generated by another PE in CE dual-homing scenarios.

PE sets the DN-bit of Type 3 and 5 LSAs and checks the DN-bit of Type 3 and 5 LSAs.

user_2790689 · Created Apr 19, 2017 07:34:55

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Adamcolob · Created Apr 19, 2017 07:38:57

If a Provider Edge (PE) device advertises Type-3 and 5 link-state advertisements (LSAs) to Customer Edge (CE) devices through area 0, the optional high-order bit of these LSAs must be set and called the DN bit. If these LSAs are advertised through an area other than area 0, the DN bit can be set or not set.

The DN bit is used to prevent routing loops. A PE ignores any LSA whose DN bit is set. This prevents a routing loop caused when a PE learns from the CE the LSA generated by another PE in CE dual-homing scenarios.

PE sets the DN-bit of Type 3 and 5 LSAs and checks the DN-bit of Type 3 and 5 LSAs.

chenhui · Created Dec 16, 2019 11:21:22

As Adamcolob, DN bit could help to prevent the netwokr loop in OSPF.@

Steelblue · Created Dec 20, 2019 08:29:32

To prevent routing loops, an OSPF multi-instance process uses a bit as the flag bit, which is called the DN bit.

What Is the Purpose of Setting the DN Bit in an OSPF LSA?

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What Is the Purpose of Setting the DN Bit in an OSPF LSA?

Third Party’s Trade Secret

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